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10EXPERIENCE OF DRILLING EXPLORATION WELLS IN DIFFICULT GEOLOGICAL CONDITIONS AND MASTERING THEM BY THE METHOD OF DUAL COMPLETION
OPERATION
Deryaev A.
Candidate of Technical Sciences, Senior Researcher, Scientific Research Institute of Natural Gas of the State Concern „ Turkmengas", Ashgabat, Turkmenistan https://doi.org/10.5281/zenodo.6992262
Abstract
The article discusses the drilling of a prospecting and exploration well in difficult geological conditions. The design of the well and recommendations for drilling fluids are given, as well as the result obtained during the development of the method dual completion (DC) by two elevators with pumping and compressor pipes. When drilling this exploration well, the design was changed from the previously used conventional design for the Northern Goturdepe field. This work can be used for drilling deep wells in fields with complex mining and geological conditions and abnormally high reservoir pressure, in order to accelerate the development of multi-layer deposits.
Keywords: inhibited solution, collapse formation, tack, shank, water-based solution, blowout equipment, black clay.
When choosing and justifying the design of the North Goturdepe well № 37, the requirements of the "Safety Rules in the Oil and Gas Industry", the Regulations for calculating intermediate columns when Drilling wells in the oil and gas fields of the Western Part of Turkmenistan were taken into account and geological and technical information on previously drilled wells in the North Goturdepe field was used.
The choice of the well design was carried out in accordance with the intervals of compatibility of the well section according to the mining and geological drilling conditions, based on the forecast curves of reservoir pressure of rock rupture, and the following design was justified.
- the shaft direction 0 720 mm descends to a depth of 10 m, is fixed with butobeton.
- the elongated direction of 0530mm descends to a depth of 30 m, in order to overlap unstable, sandy-clay deposits and prevent erosion of the wellhead when drilling under the conductor. The height of the cement lifting is up to the wellhead.
The conductor 0426mm descends to a depth of 594 m, provides overlap of the upper part of unstable sandy-clay quaternary deposits, isolation of the borehole from hydrostatically connected waters with the surface and installation of anti-blowout equipment.
The 0324mm technical column descends to a depth of 2781 meters to overlap the swelling and collapse of the "black clays" of the Absheron tier and to shorten the interval of the open trunk when drilling for the second technical column 0244.5 mm, was equipped with anti-blowout equipment and to ensure effective well management in case of possible manifestations. The descent of the 0324mm technical column is carried out in two sections. The head of the I section is installed in a stable part of the open trunk section, in the range of 1700-2300 meters with logging adjustments. The height of the cement rise behind the column is up to the wellhead.
The descent of a technical column with a diameter of 0244.5 mm is carried out to a depth of 4761 meters, in order to prevent the absorption of drilling mud with a density of 2.08g/cm3 and the seizure of drilling tools under the influence of pressure drop, as well as effective well management during manifestations using blowout equipment. The descent of the 0244.5mm technical column is carried out in two sections, and the head of the I section was installed with a 50-100-meter approach into the 0324mm technical column.
The descent of the operational filter shank 0177.8mm is carried out to a depth of 4906 meters along the trunk (the length of the shank is 4691m-4906m), by installing a suspension device for 50-100 meters inside the casing 0244.5 mm in order to overlap productive horizons [1].
The complex thermogeochemical conditions of drilling well №37 of the Northern Goturdepe field cause, from zero to the design depth, the need to use drilling fluids with a reduced water output and easily adjustable rheological and structural-mechanical parameters.
Water-based drilling fluids with an interval change of the type of chemical treatment, providing for a smooth transition from solutions stabilized with sodium - humates and lignosulfonates, are transferred to inhibited systems of alumocalcium solutions -ALKAR-3M
Temperature ranges of drilling fluids application:
- Oil-emulsion humate-lignosulfonate solution -+22 - +40 °C;
- Alumocalcium solutions - ALKAR-3M- +40+121 °C.
Oil-emulsion humate-lignosulfonate solution is used from the beginning of drilling until its effectiveness drops. With a decrease in the effectiveness of the oil-emulsion humate-lignosulfonate solution, the transfer to the inhibited solutions of the ALKAR-3M system is carried out.
When drilling a well, starting from zero to a depth of 800 m, an oil-emulsion humate-lignosulfonate solution is used to drill unstable sand-clay rocks of the quaternary deposit and stabilize the wellbore.
Stabilizers reagents are used as regulators of the properties of the drilling mud: humates - coal-alkali reagent (KAR) and ligno-sulfonates - condensate of sulfate-alcohol bard (KSSB-2). Caustic soda (NaOH) is used to regulate the alkalinity of the calcium solubility solution in seawater. Oil and graphite are used from specialized reagents functionally designed to hydro-phobize the solid phase of drilling mud and improve lubricating properties. To prevent foaming of the solution, a surface-active substance is used - surfactant HT-48. The hydrogen pH of the solution is 8.5-9.0 [2].
In the future, the processing of an oil-emulsion hu-mate-lignosulfonate solution is carried out in order to reduce the viscosity of the solution and water loss to the
set values of the parameters. If the pH of the solution falls below the value, the required amount of NaOH should be introduced into the solution. Preparation and addition of reagents in the future is carried out as needed.
When drilling a well from a depth of 800 m to a depth of 2800 m, an inhibited ALKAR-3M solution is used. This solution is used to cover high-colloidal "black clays" of the Absheron tier, prone to collapses. ALKAR-3M suppresses the lyophilicity of clays, reduces the accumulation of excess volume of drilling mud and at the same time provides stability and strengthens the walls of the borehole.
Information on the recommended parameters of the drilling mud, when drilling for each column of the well №37 Northern Goturdepe are set out in Tables 1 and 2.
Table 1.
Types and parameters of drilling fluids for drilling exploration well № 37 of the Northern Goturdepe field
Name (type) of the solution Interval, m Drilling mud parameters
From (top) Up to (bottom) Density, g/cm3 Conditional viscosity, sec Water output, cm3/ 30min Crust, mm Static shear stress, kgf/cm in, min
1 10
oil emulsion humate-lignosulfonate 0 800 1,26 40-60 10-12 2-3 10-20 20-30
ALKAR-3 800 1900 1,28 30-50 6-8 1-2 5-10 5-15
-II- 1900 2800 1,45 30-50 6-8 1-2 5-10 5-15
ALKAR-3M 2800 4000 1,35 30-50 3-4 0,5-1 5-10 5-15
-II- 4000 4300 1,40 30-50 3-4 0,5-1 5-10 5-15
-II- 4300 4600 1,45 30-50 3-4 0,5-1 5-10 5-15
-II- 4600 4800 1,64 30-50 3-4 0,5-1 5-15 5-20
ALKAR-3M 4800 4900 1,78 50-70 2-3 0,5 5-15 5-20
-II- 4900 5000 1,92 50-70 2-3 0,5 5-15 5-20
-II- 5000 5100 2,02 50-70 2-3 0,5 5-15 5-20
-II- 5100 5200 2,08 50-70 2-3 0,5 5-15 5-20
Reagents are used as regulators of drilling mud properties: stabilizers lignosulfonates - ferrochromolig-nosulfonate (FHLC) and KSSB-2, inhibitors - alkaline hydrolysates of Portland cement, thermostabilizers -sodium bichromates (Na2Cr207) or potassium (K2&207), alkalis - NaOH. The hydrogen pH of the solution is 10-12.
When drilling a well from a depth of 2800 m to a depth of 4800 m, an inhibited heat-resistant solution ALKAR-3M is used in the zone of elevated temperatures +113 ° C. This solution is used to suppress clays
of the lower red-colored thickness, stabilize the borehole and excessive saturation of the drilled rock. Provides stability of the solution parameters in the zone of elevated temperatures [3].
When drilling a well from a depth of 4800m to a depth of 5200m, an inhibited ALKAR-3M solution is used in the zone of elevated temperatures +121 ° C in order to suppress clays of the lower red-colored thickness and open productive layers of the well, stabilize the wellbore and excessive saturation of the drilled rock. Provides stability of the solution parameters in the zone of elevated temperatures.
Table 2.
Drilling mud parameters, when drilling an exploration well __№37 North Goturdepe field_
Name (type) of the solution Interval, m Drilling mud parameters
From (top) Up to (bottom) Phase composition, % vol. pH Mineralization, mg/l Plastic viscosity, sDr Dynamic shear stress, mg/cm2 Ca+2 mg/l
Voil Vsol yf
oil emulsion humate-lignosulfonate 0 800 8,62 77,46 13,92 8,5-9 13-15 15-18 30-33 300-400
ALKAR -3 800 1900 10,62 14,88 74,50 10-12 15-17 5-8 10-20 900-1500
-II- 1900 2800 10,62 20,60 68,78 10-12 15-17 10-12 10-20 900-1500
ALKAR-3M 2800 4000 13,21 17,24 69,55 10-12 15-17 10-12, 10-20 900-1500
-II- 4000 4300 13,21 20,15 66,64 10-12 15-17 10-12 10-20 900-1500
-II- 4300 4600 13,21 20,71 66,08 10-12 15-17 10-12 10-20 900-1500
4600 4800 13,21 28,77 58,02 10-12 15-17 10-15 10-25 900-1500
ALKAR-3M 4800 4900 13,21 33,96 52,83 10-12 15-17 15-20 15-25 900-1500
-II- 4900 5000 13,21 40,35 46,44 10-12 15-17 15-25 15-30 900-1500
-II- 5000 5100 13,21 42,70 44,09 10-12 15-17 18-25 20-35 900-1500
-II- 5100 5200 13,21 47,65 39,14 10-12 15-17 20-30 25-40 900-1500
Drilling after the descent and fastening of the technical column 0244.5 mm was carried out with a drill bit 0215.9 mm using a rotary layout and drilling mud with a density of 1,80 g/cm3. At a depth of 4953 meters, drilling reached the design horizon and 12 productive horizons of the lower red color were opened. According to the research of logging data, a cement bridge was installed in the range of 4906-4953 m and a 177.8 mm shank was lowered to test objects in opened sections to a depth of 4906 m. With the 70m entrance of the upper end of the shank 0177.8 mm into the inside of the
0244.5 mm technical column, the Weatherford shank suspension system was used to suspend and ensure the tightness of the upper end of the shank. The use of this system when the operational shank 0177.8mm was lowered led to an increase in the reliability of the quality of cementing work and the tightness of the upper end.
The figure shows the design of well №37 on the Northern Goturdepe field with a two-lift tubing with downhole equipment for DC
Figure.
Design of well №37 with a two-lift tubing with downhole equipment for the DC at the North Goturdepe field
During the development of the well by the DC method, a large inflow of oil was obtained, the results of the studies are shown in Table 3.
Table 3.
Data on perforations and indications of studies during the development of well №37 of the Northern Goturdepe
field
Object designation, type of perforator, number of holes Distance of the test object, (m) Age, artificial depth, (m) Development results
I PKO -102 733 4448-4454 4612-4618 4626-4629 NK-7 NK-8 Oil inflow was recieved. Dconnect. pipe =25mm, Pwork =35 atm. Qoil =730,33 m3/day.
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