CC BY
65
Fig. 2. Show Desktop drying device raw cotton
On Fig. 2: 1 - raw cotton; 2 - rack; 3 - block radiators; 4 - conveyor belt; 5 - clips; 6 - hopper for feeding of raw cotton (the arrows indicate the direction of movement of the conveyor belt).
Total installation — 7500 mm. length, width — 1500 mm., height — 2200 mm. The speed of the rotating movement of the conveyor belt 0.25 m/s. With such a belt speed, in the drying installation with 7.5 tons of seed cotton per hour allows wherein reduce humidity of 2-3 %.
Currently, the ginneries mostly installed two gin (voloknoot-delitelnye machine) brand of DP-130 or DPC-180, the performance of which, depending on the varieties of raw cotton is 12-14 m/hour.
If necessary, depending on the level of raw cotton moisture can change the intensity of the infrared radiation, the length/width or speed of the conveyor belt.
References:
1. 2.
3.
4.
5.
Lykov A. V Drying theory. - M.: Energia, 1968. - 472 p.
Saidov M. S., Ashurov M. H. Pottery with two-pulse energy barrier and thermal radiation//Solar technology. - T.: 2002. - № 3. - S. 69-73. Rakhimov A. D., Saidov M. S. Ceramic converters of solar energy in the therapeutic infrared radiation//Solar technology. - T.: 2002. - № 3. - S. 74-77.
Rahimov A. D., Ermakov V P., Mahamedova M. A. Application of functional ceramics, synthesized in the Big solar furnace in the drying process//Solar technology. - T.: 2002. - № 4. - P. 69-73. Pat. Statement №IAP 2011 0506. 06.12.2011. iskh. № 11468.
Romanov Andrey Aleksandrovich, LLC «AkvaStroyMontazh», Saint Petersburg, Russia, Director General E-mail: asmvoda@yandex.ru
Use of unplasticized polyvinyl chloride (uPVC) casing pipes in water supply well construction
Abstract: The article contains the information about the practical experience of the use of unplasticized polyvinyl chloride (uPVC) casing pipes in water supply well construction as exemplified by the work of LLC «AkvaStroyMontazh», one of the pioneers of this technology in the northwest of the Russian Federation. The development of the technology is described in detail: the reason of its appearance, difficulties faced in the process of its implementation, obtained economic effect and a broad range of non-economic advantages.
Keywords: Water supply well, uPVC pipes, well construction, well installation, well deviation, drilling mud.
The article presents Russian experience of the use of unplasticized polyvinyl chloride (uPVC) casing pipes in water supply well construction. The use of plastic pipes allows accelerating the performance of works, reducing their production cost and human factor effect. A technology of well drilling in the shifting soil was developed for the purpose of successful application of uPVC pipes in the drilling works on the territory of the Leningrad region.
The importance of the underground waters in the supply of drinking water to the population both in Russia and the world in the whole is steadily growing [3, 22-28]. This is mainly promoted by the following factors:
• pollution of the surface water sources;
• development of the so-called suburban construction and the increased significance of autonomous water supply related to it, the optimal way of installation of which is the use of underground waters;
• improvement of drilling technology.
Over 300 million water supply wells have been drilled in the world in the last 25-30 years. For instance, about a million water
supply wells, the water of which is used not only for domestic needs, but also for irrigation and technical water supply, are drilled annually in the USA [5, 1-2]. In this respect, innovative technologies for water supply well construction with the use of progressive technologies and materials are becoming increasingly important.
In Russia, well drilling, as a technological direction, generally has a powerful scientific support, which, in fact, is not homogeneous for different segments of the industry. If the researches of drilling and, broadly, construction of wells intended for exploration and extraction of raw hydrocarbon deposits engage numerous highly qualified scientific personnel, whose work results in a significant volume of innovative technical experience, the scientific support of water supply well drilling is insufficient. But, that does not mean that this direction doesn't develop — there are new technical solutions and, from time to time, real technological breakthroughs. However, their driving power most often lies in the efforts of skilled production workers who implement progressive technologies at their own risk.
The above stated fully relates to the innovative technology of hard uPVC casing pipe application for water supply wells.
UPVC casing pipes: introduction
In 2010, all drilling companies in the Leningrad region used steel pipes in the installation of wells for underground waters extraction. While uPVC casing pipes had been successfully used abroad for several decades, in our country, information about the technology using uPVC pipes was in the form of fragmentary non-systematized data. The author of the article, a certified engineer-hydrologist, became interested in the new technology.
Already at the first stage of familiarization with uPVC casing pipes, it became obvious that the application of these pipes in lieu of the traditional steel pipes was a promising direction. Gradually, a whole complex of tasks that could be solved by such an effective tool as uPVC pipes came up.
Firstly, the comparison of plastic and steel pipe prices suggested that the replacement of steel pipes with the plastic ones would lead a significant reduction of capital costs on well construction.
Secondly, the use of plastic pipes promised to significantly enhance the pace of works on well installation, increase the productivity of the company's work in the whole and reduce the time of performance of certain orders.
Thirdly, the application ofuPVC pipes leads to the improvement of production culture, reduction of hard manual labor, because plastic is much lighter than steel. Reduction of the material weight notably facilitates the logistics: there is an opportunity to withdraw from heavy multi-ton vehicles because the delivery of plastic pipes to the site can be performed even by a low-capacity pickup truck. Plastic pipes are easier to store; moreover, the speed of their delivery increases and the cost reduces meaning that the overhead costs decrease.
Fourthly, the use of plastic pipes allows reducing the human factor effect on drilling works as the low quality ofpipe thread often leads to the parting of the drilling string.
Altogether, the benefits from the use of plastic casing pipes allow substantively, by dozens of percent, reducing the production cost of a well. This is a sure way to increase of marginality (profitability) of business and gain competitive edge.
The increase of economic efficiency of water supply well construction is possible due to the optimal effect of all resources included in the production process, the most important of which are the following:
• staff — qualification level as well as adherence to production and technological discipline;
• materials;
• equipment;
• other means of labor.
All of them, and, most importantly, their quality, impact the end results of a drilling company operation. Expenses on materials are the most important expenditure category during well construction and a special place among them is given to casing pipes.
While choosing casing pipes today, there are, as a rule, two alternatives — steel pipes and pipes made of polymers, predominantly uPVC, and more rarely — made of polyethylene and polypropylene. Economic benefits (economic effect in monetary terms) is the main factor determining the choice.
The economic advantage from the implementation of uPVC casing pipes can be determined using a general formula of economic efficiency calculation:
where: Em — economy of current production cost;
Nm and N.mp — norms of material consumption, respectively, before and after the implementation of the event (in this case, before the replacement of steel pipes with uPVC pipes);
P and P — price for a unit of the material, fuel etc. before
m imp ^ '
and after the implementation of the event;
C and C — coefficient ofuse of material resources before
m imp
and after the implementation of the event;
Q — cumulative production.
Apart from the economic impact, a scientific-technical impact should also be taken into account: functionality, environmental safety and simplicity of use of uPVC pipes. The latter, for instance, is expressed in the reduction of loads on the staff at the expense of exclusion of inevitable use of demanding, mainly manual, labor in the case of steel casing pipes.
Significantly lower mass of polymer pipes compared with the other does not only facilitate the labor of the staff, but also has a direct economic impact. It is determined by the reduction of transportation costs that are an integral part of the production costs of well construction (see Table 3).
Comparison of the mass of steel and uPVC casing pipes
Comparison of the mass of uPVC and steel casing pipes clearly certifies about the benefit of the former. To realize this, one can use two normative-technical documents: «GOST 632-80. Casing pipes and their collars. Technical conditions (with Amendments № 1, 2, 3, 4)» and «TU 001-84300500-2009. Pipes and filter cases for wells made of unplasticized polyvinyl chloride with thread». GOST 632-80 was put into effect on January 1, 1983; in the part of pipe execution A, on January 1, 1984; its validity was extended till January 1, 1993 by the Decree № 174 of the State Standard of the USSR as of 24.01.1986. From July 1, 2003 till the technical guidelines came into effect, it and the majority of acts of federal executive bodies in the sphere of technical regulation are of recommended nature and subject to compulsory execution only in the part corresponding to the purposes specified in item 1, article 46 of the Federal law № 184-$3 as of27.12.2002.
TU 001-84300500-2009 developed by CJSC «Khemkor» came into effect on 25.06.2009 with unlimited validity.
If one selects steel pipes with external diameter of 127 mm. and uPVC pipes with a similar indicator equal to 125 mm. out of the standard series as most often used in water supply well construction, the mass of 1 linear meter of steel pipe will account for 19.1 kg. with the wall thickness of 6,4 mm, in accordance with GOST 632-80 [2, 10]; whereas one meter of uPVC pipe with the wall thickness of 6.0 mm. weighs 3.37 kg. (TU 001-84300500-2009). The correlation of the mass of a length unit of the compared pipes is almost 1:6, which means an absolute difference in the mass of a casing pipe at the length of1 m equal to15.83 kg.; at the depth of a well of 100 m. equal to 1583 kg., and at the depth of a well of 300 m. equal to 4749 kg.
Reference information Table 1. - Geometric sizes and mass of steel casing pipes (GOST 632-80. Casing pipes and their collars. Technical conditions (with Amendments № 1, 2, 3, 4)) [2, 10]
E„
N x P N x P
m m imp imp
x Q,
External diameter, mm Wall thickness, mm Internal diameter, mm Mass 1 m, kg
127 5.6 115.8 16.7
127 6.4 114.2 19.1
127 7.5 112.0 22.1
127 9.2 108.6 26.7
127 10.2 106.6 30. 7
C
C
Table 2. - Geometric sizes and mass of uPVC casing pipes (in accordance with TU 001-84300500-2009. Pipes and filter cases for wells made of unplasticized polyvinyl chloride with thread) [9, 5]
Comparison of the cost of steel and uPVC pipes
The definition of production cost of works on water supply well construction can be done by analytical way on the basis of a calculation with the use ofnormative and project documents included in the budget normative base of price formation in construction and on the basis of work experience of certain enterprises. As it is known, by the Decree of the Ministry of Construction of Russia № 31/np as ofJanu-ary 30, 2014 «About putting new state costing standards into operation» (in the revision of the order № 39/np as of February 7, 2014), a new edition of the state costing standards was put into operation on April 1,2014 and added to the federal register; it included: state itemized costing standards (GESN-2001), federal unit rates (FER-2001), collections of estimate prices on materials (FSSTS-2001).
Table 3. - Estimated distribution
Statistical information about the average cost of steel pipes and uPVC pipes can be found in open resources, although, it is quite widely scattered. It is determined by the current market situation, presence of anti-corrosion protection in steel pipes, their affiliation with the steel grade group etc. But, comparing uPVC pipes and steel pipes, similar in the exploitation character, with the external diameter of 125 and 127 mm. respectively, one can estimate approximately the absolute rates of economy gained by the producer and customer using uPVC casing pipes. As the market review demonstrates, the cost of one meter of a steel casing pipe is from 800 to 1600 rubles; whereas, one meter of uPVC pipe is from 350 to 450 rubles. Thus, one can rightfully talk about the correlation of prices 1:2 in favor of uPVC pipes. In absolute figures, one can talk about the economy of approximately 40 000-100 000 rubles in case of the length of a casing string of 100 m. and 120 000 and 300 000 rubles in case of the well depth of 300 meters.
First experience and first difficulties
There is a large distance between the «construction» of plans and their realization. Mastering of new technologies was required, but there was no-one to learn from. Drilling companies undertook single trial attempts to use uPVC pipes, but none of them succeeded in achieving a positive sustainable result. It became obvious that trial-and-error approach is not the best, but the only possible one in the given circumstances.
The use of polyethylene and polypropylene pipes (such pipes are still used today in small amounts) was the precursor of the use of uPVC pipes at «AKVASTROYMONTAZH», but it was
State costing standards. Earlier, the Provision about the structure of cost on production and realization of a product (works, services) and order of formation of financial results taken into account in taxation of profits approved by the Government of the Russian Federation № 1095 as of September 11, 1998 with further supplements and amendments was the main document in formation of the production cost of a product at the enterprise. To calculate the production cost of water supply well construction, one can use the Federal estimate prices on exploitation of building machines and collections of tariffs on cargo transportation.
Based on these documents and work experience in the market of drilling companies, one can group relative share of costs in % on water supply well construction in the form of a table 3. costs in water supply well drilling
apparent immediately that they were only suitable for the installation of small wells with the depth up to 30 meters.
The first experience ofwork with plastic pipes showed that they demand much more from the geometry of a well bore compared to the other. And, if a steel pipe is ready to «excuse» unevenness and fluctuations of the diameter gauge, the plastic one won't. The first difficulties were related to this peculiarity of pipes. Roller cone bits with the diameter of 151 mm. were used to drill wells (bore or hole) for uPVC pipe and steel pipes. Starting from the depth of 30 m., the uPVC pipe didn't «want» to go down further, while its diameter was 125 mm. (plus local thickening of 134 mm.) and the diameter of the steel pipe was slightly bigger — 127 millimeters. But, the steel pipe was going down under its own weight cutting off the unevenness. If required, it was possible to put pressure on, hammer and push the steel pipe. The use of such method with a priori «gentle» plastic pipes requiring delicate treatment is categorically unacceptable.
It developed that the well bore drilled with a roller cone bit is not as even as it seemed initially. Moreover, the diameter of the bore is not same along its length. At the expense of different inclusions, more solid than the surrounding rock or, on the contrary, soft and loose, it may narrow. The soil disturbed by drilling equipment starts moving and heaving; separate fragments fall out. Especially difficult problem was posed by the fragments of float stones, pebbles and gravel. Small stones moving in the soil caused the change of configuration of walls of the well bore and became an insurmountable obstacle for a plastic pipe. The depths up to 100 m. turned out
External diameter, mm Wall thickness, mm Mass of uPVC pipes, kg
L = 1000 mm L = 2000 mm L = 3000 mm L = 4000 mm
125 5.0 + 0.9 3.0 5.8 8.6 11.4
125 6.0 + 0.9 3.37 6.73 10.10 13.46
125 7.5 + 1.0 4.3 8.5 12.6 16.7
of
№ Cost item Relative share of cost, %
1. Primary and secondary materials
- including casing pipes 20-24
- chemical reagents 0.5-1.5
2. Expenses on drilling equipment 6-8
3. Transportation costs, including shift team transportation 10-12
4. Expenses on fuel, electric and heat energy 4.0-6.0
5. Depreciation of equipment, repair of equipment and tools, spare parts 10-12
6. Salary and social insurance 10-12
7. Environmental safety 1.5-2.5
8. Other 29-31
to be especially difficult in this respect. There could be 5-6 or even more places at every site that became an insurmountable obstacle on the pipe's way down.
It was possible to address the experience of foreign colleagues who used uPVC casing pipes. But, it emerged that even in the USA, where a vast experience of installations ofwells with uPVC pipes in solid (rock or similar in properties) materials was accumulated, the method of construction of wells in moving, poorly «keeping the shape» of the bore materials was not developed.
The simplest and obvious solution was to do ample drilling, i. e. with a roller cone bit with the diameter of161 m. instead of151 m. There was an alternative option to install a casing pipe of smaller external diameter in the well bore retaining the previous diameter of drilling equipment, but it was rejected because there could be problems with pump placement.
It should be noted that a transition from a common diameter of the roller cone bit of151 mm. to uncommon diameter of161 mm. is accompanied by the appearance of problems with the addition of cutting device to the complete set of drilling equipment as well as the need to use uncommon spare parts.
At the increase of the diameter of the well, it was required to use costlier drilling equipment; the consumption of drilling mud and fuel was augmenting; the difficulty of works was growing, but the speed of drilling was reducing as well as productive capability.
The transition to well drilling with the diameter of 161 mm. did not solve the problems — the plastic pipe was still reluctant to go down the hole ofbigger diameter. Of course, one could continue moving in this direction, switching to the use of roller cone bits with the diameter of, for instance, 190.5 mm, but it is not known, if it would help to solve the set tasks. However, it was obvious that it would lead to the increase of expenses bringing to naught the advantages of replacement of steel pipes with plastic ones.
Search for optimal drilling mud composition
It became clear that the solution of the problem of poor possibility of the hole (bore) for the plastic pipe lies not in the increase of the diameter of the well but in the strengthening of its walls. The only way to achieve it is to use a drilling mud with a required set of properties.
It is known that the creation of backward pressure on the walls of the well and prevention of caving formation are one of its most important functions.
The main question is what drilling mud to use? «AKVASTROY-MONTAZH», like many other companies, used the mud of regular Cambrian Viennese clay. Mudding of the well walls with the wash-down with clay mud during drilling in the unstable rocks is a known way of strengthening the well walls. After the injection of clay mud in the openings of the rocks and its solidification around the well bore, the annular zone of the rock strengthens. But it didn't meet the entire complex of requirement in the drilling of wells for uPVC pipes.
It is known that to eliminate the problem of swelling and destruction of the well walls, polymers are added to drilling muds. For instance, partially hydrolyzed polyacrylamide (PHPA). Creating a polymer film on the surface of walls and isolating «opened» rocks, polymers make the hydration and/or disaggregation of clays slow down. However, the use of these polymers is limited because, in case of their big concentration, the muds become too viscous and lose workability [1, 99-108].
Silicates are also added to drilling muds intended to strengthen the walls.
It was decided to use the experience of horizontal directional drilling (HDD); similar problems were faced, but we learnt
how to solve them quite successfully. Moreover, a classic chart of drill penetration rate dependence (Vm) on wash-down mud consumption (Q) and optimal composition of different components in drilling muds depending on the rock properties were taken into account.
Fig. 1. Examples of impact of different concentrations of extender and soda ash mixtures on the indicator of mud filtration
Fig. 2. Impact of drilling mud consumption Q on drill penetration rate VM
The chart (Fig. 2) shows that the increase of mud consumption is effective only until it reaches some value Qg; at QMax> mechanical penetration rate stabilizes. The value Qg depends on the structure of a bore bit, scheme of bottom-hole cleaning, specific axial stress, rotation frequency, rock hardness and drilling mud properties.
«AKVASTROY» considered the experience of drilling mud producers conducting independent research works and determining optimal compositions of drilling muds for drilling of various rocks based on their results (Fig. 3).
40
35
30
E 25
20
8 15 c o O
10
eh Soda ash □ Bentonite e Lubricant
v!
£
X;
X;
¡KSS SJKS nrr- JSSJ rr^ 55S1 r^
Clay Clay loam Sand clay Sand Gravel
Fig. 3. Optimal contet of separate components of drilling mud depending on the composition of rocks (accoding to the data of «Soyuzoptokhim»)
The analytical study of a big volume of special information resulted in making a decision to try bentonite clay that easily dissolves in water and expands by 7-8 times on contact with it.
Bentonite clay of the highest quality is extracted in Texas, USA. «AKVASTROYMONTAZH » acquired a few dozens of kilograms of mud produced based on its composition. Although, its cost was much higher than the common Cambrian clay, the positive effect turned out to be impressive. The well drilled the day before completely preserved its geometry even the next day, 10 and more hours after the removal of drilling string, which allowed easily inserting an uPVC pipe in it.
This result was not achieved immediately; the drilling mud based on bentonite clay was supplemented by special additions giving it unique properties. Structure-forming agents, modifiers of rheological parameters, reducers of filtration, stabilizers, lubricants, liquifires and biocides were used as additives.
Thus, high retaining and bearing capacity during drilling was ensured. And now, even at big depth of the well, its walls retained a stable form, which is so important for plastic pipes. The use of vis-cosifiers and fluid-loss reducers regulating the viscosity of the mud did not only reduce the consumption of bentonite, but also helped the formation of solid and flexible film on the walls of the well bore, which is the guarantee of competence even of such problematic soils as running ground and water-cut sand rock. Moreover, additions in the bentonite clay mud contributed to the improvement of cleaning of the well bore, prevention of sticking of small particles to drilling equipment, stimulation of removal of drilled rock, including the problematic small stones mentioned above.
Choice of drilling mode
Even during the drilling of wells with the application of quality drilling mud, there were situations when the inserted pipe started resisting upon reaching 60-80 meters. This, most probably, meant that starting from this point, the bore of the well was nonetheless deflected. This speculation confirmed the repeated drilling with the use of a basket bit because from this very place, a drill equipped with a basket bit started drilling from the actual beginning correcting the «geometry» of the bore that had gone aside.
Although, uPVC pipes possess high mechanical performance in respect of contraction and extension, natural, i. e. self-induced deflection of the bore from its design direction, can become a big problem in construction of water supply wells with the use of uPVC pipes. At
self-induced deflection ofthe bore, design bottom-hole pattern is violated; the running-in ofcasing pipes becomes difficult, especially at the sites of abrupt dog-legs. There are also adverse effects:
• extension of the bore;
• increase of consumption of power on drill string rotation;
• complication of control of load on the bore bit;
• increase of the cost of construction of the well compared to the cost of conditionally vertical one;
• at the deflected sites, inter-repair period (IRP) of pump equipment reduces significantly [4, 4-6].
Deflection of the well in the process of drilling, as a rule, is determined by one of the three groups of reasons: geological, technological and technical, influencing both, spatial well location and intensity of its deflection.
Geological factors influencing the deflection of the well include:
• anisotropy of rocks;
• texture and structure of rocks;
• structural-tectonic conditions of bedding of rock layers;
• alternation of rock layers of different hardness (in case of increase of frequency of alternation of rocks of different hardness, the intensity of deflection of the well increases) [8, 12-24].
Technical factors include the way of drilling, correctness of installation of a drilling machine, form of placement and exit of teeth and way of creation of axial load on the bottom hole.
Technological factors of well deflection include factors determined by the technology of drilling. Primarily, there are defined regime parameters: axial load on the bore bit, frequency of its rotation, consumption and quality of drilling mud as well as the way of drilling. The biggest difficulties in the struggle with well deflection come up at rotational way of drilling [8, 30-32].
Today, different regularities of impact of technical-technological factors on the deflection of drilling wells have been revealed.
The direct effect on it is created by:
• number of cone rollers and bit blades;
• construction ofbore bit, bore bits of cone roller type deviate the well bore by bigger value than cutting bore bits.
Type and construction of the bore bit primarily influences not the direction but the intensity of deflection of the well bore.
A number of rotations of the bore bit and mechanical rate of drilling are more significant factors.
The impact of the frequency of the bore bit rotation determined by the possibility of buckling of the drilling string under the effect of centrifugal force is two-base. On the one hand, as the frequency of rotation increases, the values of deflection force affecting bore bit augments. On the other hand, the stability of the pipe enhances, i. e. it resistance to the change of axial direction leading to the reduction of deflection grows.
Deflection processes intensify with the increase of axial load, which is the main factor determining the intensity of rock destruction. With the growth of axial load on the bore bit, the degree of bending of the bore bit relative to the well axis increases. Moreover, increase of axial load on the bore bit enhances the development of well walls, which also leads to a more intensive deflection of the bore hole.
At least 2/3 of costs on drilling and well casing depend on the duration of the drilling, thus, it is not surprising that the growth of the drilling rate is considered as one of the most obvious ways of reduction of well production costs. The dependence of the drilling rate on the axial load on the bore bit is not same for different rocks (Fig. 4).
Fig. 4. Dependence of the drilling rate (vm) on the axial load G for different rocks: 1 - soft rocks; 2 - rocks of medium hardness; 3 - hard rocks; 4 - solid rocks
The higher the axial load is, the bigger the mechanical drilling rate is. The mechanical drilling rate under the axial load and constant rotation rate increases faster than in case of the increase of the rotation rate under constant axial load. Ideal curve (in this case — direct line) of the dependence of mechanical drilling rate on the axial load on the bore bit looks as follows (Fig. 5):
Fig. 5. Dependence of the mechanical drilling rate on the load on the bore bit
The dependence of the mechanical drilling rate on the angular rotation rate of the bore bit is shown on Fig. 6.
Fig. 6. Dependence of the mechanical drilling rate on the angular rotation rate of the bore bit
In a greater degree, the curve corresponding to the reality has a more complex appearance. Its site Oa corresponds to the surface destruction of the rock, and sites ab and be — to fatigue-volume and volume ones respectively. Fitting of the curve at the sites Oa and
ab is mainly determined by the regularities ofrock destruction, and at the site bc, apart from them, by the geometry (primarily, by the height of working elements of the bore bits) of teeth of the cutting tool.
As it is known, power dependence of the mechanical drilling rate v on the load on the bore bit G [10, 248] and its rotation frequency n was obtained by empiric way (herewith, there were forced vibrations of the bore bit [7, 27]); the dependence: v = a ■ nx ■ Gy ,
where the values of a, x andy are defined by the properties of rocks [11, 215]. For instance, in case of a turbine drilling in the rocks of Kashirskian set x = 0.7; y = 1.1; a = 0.0024 [6, 2-3].
Fig. 7. Dependence of the mechanical drilling rate on the axial load on the bore bit
By the way, the mechanical drilling rate depends not only on the properties of the rock, but also on the degree of cleaning of the bottom hole of the well.
Ineffective removal of sludge leads to the reduction of both, mechanical drilling rate and to the fact that this function reaches maximum at lower values of axial load.
Fig. 8. Dependence of change of the mechanical drilling rate vM on the axial load Pperm and presence of sludge in the drilling well
Figure 8 shows that the curve 1 corresponds to drilling under absolute cleaning of the bottom hole of the well; the curve 2 — to the so called normal position at the bottom hole of the well, when sludging-up of the well does not exceed of the height of the lowest teeth of the roller cone bit; the curve 3 — to drilling under the unsatisfactory wash-down of the well.
The aim to increase productivity in drilling with roller cone bits forces the drillers to speed up the regime of drilling at the expense of increase of axial load on the bore bit and reduction of rotation rate, which leads to reduction of amortization of the bore bit. At the same time, the increase of axial load contributes to the increase of intensity of deflection. This is the problem we faced in our company.
Fig. 9. Dependence of R i for different diameters of the well bore
After several natural experiments, the reason of well deflection was detected. It was so called «squeezing», excess, not corresponding to the torque of drilling equipment, load on the bottom hole of the well. To eliminate this problem, drilling was done without additional load created by the hydraulics (so called «leaning» drilling).
Withdrawal from squeezing that provoked the deflection of the well bore was a not less important factor to ensure straightness of wells compared to the use of bentonite drilling mud.
An obstacle in the form of a stone on the way of the drilling equipment can be another reason of deflection of the well bore. The optimal way to overcome it is to carefully cut it out with the core bit and, then, continue drilling with the roller cone bit.
The permissible radius of deflection of water supply wells is determined considering various factors.
Firstly, it is a minimally permissible radius of bore deflection calculated on the basis of conditions of possibility of all equipment along the well. Herewith, it is taken into account whether the running-in of the equipment and casing pipes is possible under the effect of their own weight. The minimal deflection is permitted, but, naturally, without remaining deformation. If the forced running-in is not possible, there should be a gapping between the equipment and walls of the well, the size ofwhich is accepted equal to 1.5-3.0 mm. In general case, the minimal radius of deflection Rmn , from this point of view, is defined quite precisely under the formula:
R - L
min 8( D - d - k) where: L is the length of the run-in equipment, m; d — its diameter, m; D — diameter of the well or internal diameter of the respective casing string depending on the initial conditions of calculation, m; k — required gapping, m.
Secondly, to avoid the destruction of well walls during the operations of running-in and lifting, the minimal radius of deflection R should satisfy the following condition:
PI
R > F '
perm
where: P — straining of the drilling string under the lifting of the equipment, kN; l — distance between locks, m;
F — permissible force of application of the lock to the
perm L 11
well wall, kN.
At depths up to 1000 m, F = 10 kN, in case of solid rocks,
i! ' perm ' '
F can be extended to 40-50 kN.
perm
Thirdly, for the normal exploitation of drilling and casing strings, i. e. to avoid the excess of permissible values of stress in the pipes at the expense of bending in the deflected intervals, the minimal radius of deflection Rmin should be as follows:
E • d
R:. =
2 [
where: E — modulus of elasticity, mPa/mm 2; d — external diameter of pipes, mm; [Sbend] — permissible stress of bending, mPa/mm 2.
Having defined the minimal radii under the formula, one chooses the biggest, based on which the following design is carried out.
The experience presented in the article is another proof of a known thesis — «Walk and ye shall reach». The fact that the technology of construction of water supply wells has tendency for wider use of uPVC casing pipes is certain. The experience of those who made first, meaning, most difficult and important steps on this path are especially significant.
References:
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2. GOST 632-80. Casing pipes and their collars. Technical conditions (approved by the Decree of the State Standard of the USSR № 2578 as of 05.06.1980 № 2578).
3. Zetsker I. S. Underground waters as a component of the environment. - M.: Nauchnyi mir, 2001.
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Rosaboyev Abdukodir Tuxtakuziyevich, candidate of sciences, the scientific institute of mechanization and electrification of agriculture E-mail: Rosaboev61@mail.ru
Imomqulov Umidjon Boqijonovich, junior scientist, the scientific institute of mechanization and electrification of agriculture, E-mail: umid210384@mail.ru
Substantiating theoretically the parameters of the blade in-built in the drum group of shelling installation
Abstract: In article results that the curve-lined external let's substantiated dimensions of curve-lined external of the blade laterals, which has curve lined externals, mounted inside the drum of mobile shelling installation; in a purpose to form a curve-lined external by means of integral graphics method let's divide into parts the second order differential formula are resulted. As obtained calculations show that the curve-lined external of the blade laterals that means the externals of left side lateral radials are equal to R = 1601.0 mm., R2 = 339.0 mm., R3 = 159.02 mm.; R4 = 186.84 mm. and R5 = 601.5 mm.; the slope angles ax = 24° 28', a2 = 27° 09', a3 = 31° 49', a4 = 27° 08' and a5 = 31° 49'; the length Lh = 552.4 mm.; as above said the right side lateral is in the same formation with the drum wall and its length is unchangeable i. e. — Ll = Lh.
Keywords: agricultural seeds, mobile shelling installation, semi machine screw shaped blade, blade having curve lined externals, shelling, technologic process.
It is known that seeds of a certain agricultural sowings having improper formed structure and due to not a higher level of its free-running, will not give to seed at lower rates or exactly hole by hole on a ground. Considering these matters, in a purpose to make round formation and increase the free-running of agricultural crops it is proposed to implement shelling technology by using protecting-feeding compounds [1].
After applied the proposing shelling technology the round shaped higher level free-running seeds as well as almost with the same geometric sizes seed grains will come out. In its turn it will facilitate seeding the agricultural crops' seeds having improper formed structure and not a higher levelled free-running, at lower rates or exactly hole by hole on a ground.
On a basis of the shelling technology of agricultural seeds, the process of shell layer forming are carried out in due sequence order. In effort to form the shell layer the seeds firstly will be moistened by using glue and promoting typed liquid. In the shelling process the seeds inspired by the centrifugal force as well as at the account of sticking glue typed liquid begin to act together with the drum group basement and walls. The seed grains motion in proper way will result in unequal distribution of treated chemicals and shelling layer forming fistular fillers above side of seeds. It outcomes in not complete finishing the shelling technological process of the agricultural crops' grain seeds in the shelling installation and the smooth covering will not be formed at grains seeds externals [2].
Considering all above it is proposed to mount the semiscrew typed blade inside the drum group of shelling installation [3]. The
semiscrew typed blade together with drum group basement and walls selects out the acting grain seeds and thus it disturbs the sequent order. But due to that the lower side of the semiscrew typed blade has a straight lined external and mounted crosswise to grain seeds action, the grain seeds are knocked to the blade at higher strength and their motion direction changes.
Due to that the semiscrew typed blade is mounted inside the drum group at j = 16-25° degrees angle than the vertical axis, the grain seeds stop moving at the culmination peak, the angle rate equals to zero. In the event if semiscrew typed blade is installed at small angle than the vertical axis, the moving distance of the seeds inside the drum group will shorten and the layer of unmov-able seed drains will be formed. In such cases a certain part of seed grains is not equally be separated together with protective feeding mixtures but it results in not perfectly and completely implementation of the shelling technologic process at required level.
Taking into consideration of all above specified it is proposed to mount the blade with curve-lined externals inside a drum group of the mobile shelling installation. Proposed the blade with curve-lined externals sticks to the drum group basement and walls; by not decreasing the angles rate of the moving seed grains it separates them from the drum group basement and walls and in this case it disturbs the its sequent order motion. In effort for the curve-lined blade to separate the grain seeds from the drum walls completely it is necessary to fabricate same with drum wall as well as it doesn't shorten the distance occurring along with around the wall sides of the drum unit, should provide changing in movement direction.
