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14USING HIGHLY MINERALIZED WASHING FLUIDS ON WELL DRILLING IN THE AREAS OF UZBEKISTAN
Umedov Sh. Kh.
Tashkent State Technical University
In contrast to other minerals oil and gas fields are opened by drilling wells, as a result of what the confidence of their reserves will be confirmed. Drilling deep prospecting - exploring and production wells in all oil gas perspective areas of Uzbekistan.
The depth of wells, depending on the area of boring varies from 1500 to 6000 m. Various geological complications: catastrophic loss of returns, collapse of muck, influence of high-pressure water-bearing bed with high content of corrosive components occur during the drilling. Stratums with anomalous high pressure (AVPD) and anomalous low stratum pressure (ANPD), exceeding hydrostatic pressure column of water for 2 times.
Well drilling is an important direction of petroleum and gas industry, and one of the complicated and capital-intensive processes. As drilling is accompanied by circulation drill fluid, drilling agent must meet definite technological requirements, which depends on mining and geological and technological conditions of drillable areas, fields [1]. Drilling agents are characterized by physical-chemical properties: density (P), plastic viscosity (n), fluid loss (B), thickness of crust (K), statistic (©) and dynamic shift voltage (t0), day's residue (O), stability (C), conditional viscosity (T) and others.
Successful well drilling in many respects depends on conformity of feature and type of drilling agent to geologic technical conditions. Drilling agents mainly divides into fresh and mineralized, on water and hydrocarbon base, weighted and non-weighted. Along with it, they are subdivided according to the structure. In turn mineralized drilling agents are subdivide into poor mineralized, average mineralized and highly mineralized. The level of mineralization of the agent is estimated by the content of salts in the water tempering. For the poor mineralized solution total mineralization of water is 5%, average mineralization 5-10%, highly mineralized - more than 10%.
Stabilized drilling agents are called such agents, treated by different chemical reagent for improving consistency of their features in the different thermobaric conditions. Drilling agents not treated by chemical reagents are called un stabilized.
For the stabilization of features of the drilling agents, prepared on the sweet and mineralized water, exist countless numbers of chemical reagents. Meantime, they are interchangeable. Each district, region, depending on existing materials, geological conditions, use worked out contents (receipts) of agents.
Solutions prepared on sea-water, which mineralization is 4-5% are used on drilling wells in seas, areas near to sea and islands. If there are salt deposits, layers contained highly mineralized water in the geologic profile, in such case, salt enriched drilling agents, stabilized by salt-tolerant reagents are used for hole making [2].
Stabilization of drilling agents salted base is more difficult then agent prepared on fresh water base. Giving technological features, meeting requirements of drilling on salt deposits to the mineralized agents, requires special chemical reagents.
A lot of organic and synthetic reagents for stabilization technologic features of drilling agents are known at the present time. But only some of them, are effective on affecting temperature and salt aggression.
Many scientist from Uzbekistan and foreign countries were engaged in studying features, working out content of mineralized drilling agents, their preparation in the mineralized water (sea water), synthesizing salt-tolerant reagents. Particularly this questions found its reflection in the works of such scientists as A.Aminov, V.S.Baranov, V.D.Gorodnov, N.Yodgarov, S.Yu.Jukhovitskiy, I.I.Klimashkin, M.Mirzaev, U.D.Mamadjanov, M.K.Turapov, Walter F. Rogers and others.
For reduction water loss of agent Walter F. Rogers recommends organic reagents of the type of carboxymethyl cellulose (CMC), starch, kverbracho, carragheen moss and others. In the above stated work was noted that, salt was undesired contaminant in the drilling agents. Even small contaminants of salt in the liquid mud, prepared in the fresh water increases water loss and statistic shift voltage (SNS). It complicates preparing steady drilling agents, containing big percent of salt. Ordinary clays for preparing solutions in the salted water are ineffective. Special salt-tolerant clays (paligorskit), which creates structure of liquid mud in the salted water for this purpose.
For lowering water loss of hard mineralized drilling agents, were recommended such reagents as modified starch (3-4%), CMC (1,5-2,0%), hydrolized polyacrylonitrile (GIPAN), metas (1,5%). Under high temperature (150-2000C)-CMC-500, CMC-600, GIPAN, carbofen, carbonyl.on combination of reagents, their usage reduces for half.
The greatest difficulties arise on simultaneous mineralization of solutions with cations, of one and divalent metals, causing coagulation, increasing water loss and others. The most aggressive is combination of ions of calcium and natrium, weaker aggression is caused by salts of magnesium. In such cases the only reagent - stabilizer is starch, but its expenditures will be greatly increased as a result of its insufficient effectiveness.
Consequently, we can make conclusions from the above given information, that listed polymeric reagents also devoid separate defects. For example, if they are steady to salt influence, then not steady to high temperature, or contrary, not steady in the mineralized environments.
Based on above stated, authors set a problem - to take new water-soluble polymeric reagent from the wastes of acrylic material for processing drilling agent, prepared on formation water with high mineralization.
In the laboratory conditions was synthesized a reagent, which base were wastes of carpet weaving factories, mainly containing polyacrylonitrile.
For receiving polymer of higher molecular weight product of alkaline hydrolysis of acrylic materials carried over polymerization in the presence of radicals - ionic initiator persulfate ammonium (NH4)2*Si2O8. Reaction occurs in the alkaline medium pH>12. Soda ash (Na2CO3) for connecting ions of calcium and magnesium, forming with polyvalent cations insoluble contaminant are entered to this mixture.
New polymeric water-soluble reagent for the first time was used for processing drilling agent, prepared on formation water during drilling well No. 13 in the area Surgil (Ustyurt). Well was set with conductor of the diameter 299 mm to the depth 338 m and cemented till collar. Well of depth 1585 m, was drilled with using boring solution, prepared fresh transported water. Protection casing 0 219 mm was dropped and cemented. Lower bottom of column 0 219 mm, with depth 1585 m, till project depth 2970 m, well was drilled with solution, prepared on mineralized formation water, with density of 1050 kg/m3, produced by air lift from water well. Initial drilling agent had a water loss 30 sm3/30 min, viscosity - 35 s, density 1240 kg/ m3.
2% reagent NPWR was input to solution and after mixing in clay mixer, solution had water loss 10 sm3/30 min, conditional viscosity - 45s. During the process of drilling, a 0.5% reagent NPWR was added to circulating solution. The well was drilled till 2970 m, and left for making geophysical investigations. Then casing pipe 0 140 mm, was dropped to the reached depth. During the process of round-trip operations, tightening and landing of drilling equipments was not noticed. Geophysical instruments also reached bottom without barrier. Drilling agent, processed by NPWR, had following indexes: density - 1240-1260 kg/m3, viscosity 40-60 s, water-loss 10-12 sm3/30 min. During the well drilling 16 t of new polymeric water-soluble reagent was used.
Well No. 21 of area V.Berdakh was drilled with solution, prepared in fresh water from Muynakskiy water supply point. Conductor was let down to the depth of 370 m. Solution had following characteristics: density - 1200 kg/m3, viscosity 40 s, water-loss 15 sm3/30 min. Due to deficiency transport means in the depth of 1878 m, it was decided to use water from the hole, drilled near the boring. For this purpose was prepared new reagent NPWR on the arrangement, prepared and mounted in the control base in Kungrad city. Bentonitic solution, processes with new polymeric reagent was prepared on formation water. After preparatory works subdrilling were continued. Solution had following indexes: ^=1220 kg/m3, T=40-50 s; B = 10 sm3/30 min. The well was successfully drilled till the depth of 3070 m, set with flow string and put in exploitation. After perforation of column, industrial inflow of gas was taken without difficulties, which indicates lack of obstructions in the pore channels of collector. Consequently, NPWR promotes preserving natural collector features of layers.
Wells No. 6 and 20 in the area Berdakh, where the imported fresh water was changed to water from wells, were drilled on same receipt. Drilling agent, processed with new reagent, had indexes corresponding to the project data. Problems related with failure and swelling the layers did not arise during drilling. Solution was stable and didn't require frequent processing. 10 tones of NPWR (10%) was spent for deepening 1235 m.
Deepening of well No. 1 of Karakum area with 2020 m., was made with solution prepared on mineralized water according to above stated receipt. Solution had following indexes: density: 11801200 kg/m3; conditional viscosity: 60 s; water loss: 10 sm3/30 min. With using of this solution the well was drilled till the depth of 4240 m., well was set a column of 0 140 mm. 20,5 tones of reagent
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NPWR was spent. Round-trip operations were made without tightening and seats. During the drilling process, water solution NPWR 0,2-0,4% from the capacity of solution (to the dry substance) was added to circulating solution. Oil in amount of 5-7% was added to solution as an lubricating component. The temperature in the depth of 4200m, was 115-120 0C, Reagent NPWR was compatible with reagent CMC, K-4.
REFERENCES
1. Bulatov A.I., Magazov R.R., Shamanov S.A. Influence of indexes of features of the drilling agent and their types to the speed of drilling // collection of scientific works of the scientific technical center LLC "Kubangazprom".-Krasnodar, 2001. S.92-103.
2. Theory and practice of well completion. Bulatov A.I., Makarenko P.P., Budnikov V.F., and others. V 5t.-M.:1997.T.1.S.29-4, T.2.S.60-90.
3. Roger V.F. Washing fluids for drilling oil gas wells. -M.:Statetoptechnical publishing house, 1960-234 s.
WASHING LIQUIDS WHEN OPENING PRODUCTIVE LAYER WITH ABNORMALLY HIGH PORE PRESSURE
Umedov Sh. X., Akramov B. Sh., Egamberdiev B. Sh., Gapporov J. B.
Tashkent State Technical University
Opening layer with abnormally high pore pressure (AVPD) is in most cases connected with intensive oil-gas and water showings, which bring out gas ejection-fountain. Fasten borehole in condition abnormally high pore pressure not less, in a complicated way, than drilling this horizon. Often happens annulus oil and gas showings after cementing. These phenomenon specialists are explains differently.
In recent years in oil and gas regions Uzbekistan, particularly in Bukhara - Khiva, Surkhandarya and Fergana oil and gas areas are accepted measures on improvement of technologies of the opening, drilling layer with AVPD and their fastening. Designed technology of the drilling high-permeability reef of the formation with AVPD on mode, close to balanced, in system layer-borehole on methods two drilling fluids. The new reagents are used for processing drilling fluids with high density.
The special field researches are conducted for determination parameter and mode priming drilling fluids for each borehole for the reason ensuring the normal opening layer.
Opening and drilling productive horizon on AVPD is realized with drilling mud heaver. Density washing liquids varies within 1,6 - 2,25 g/sm2. The preparation such drilling fluids with rheological and technological characteristics, meeting the demands technologies of the drilling in complex condition, presents the significant difficulties, but maintenance their parameter in process of the drilling else more complicated. The difficulty of the regulation characteristic washing liquids with high density is concluded in that contents dispersed phases in drilling fluids is reached greater values and accordingly decreases the amount of the dispersion ambience.
To get drilling fluids with high density is added weighting additive - barite, sometimes hematite or magnetite. There are different compositions of washing liquids, which applicable for drilling on area with AVPD.
The principle scheme of the preparation drilling fluids with density 1,60 g/sm3 are above concluded in following:
Prepares bentonitic liquid mud with density 1,15-1,30 g/sm3 on water base, which is processed reagent - fluid loss reducer (stabilizer), but then reagent-viscosity reducer (structured-mechanical characteristic). Hereinafter, in this drilling fluid added accounting amount weighing agent, and carefully mixed in special mechanical or hydraulic mixer. If it is required, coming from analysis characteristic of weighted drilling mud, in addition added reagents.
