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RECOMMENDATIONS ON THE USE OF DRILLING FLUIDS FOR DRILLING WELLS DUAL
COMPLETION
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.6912954
Abstract
The article deals with the use of drilling fluid for the inter-interval drilling of exploratory wells (directional and vertical). The point-to-point application of the ALKAR-3M drilling fluid and the Versadril type hydrocarbon base solution is highlighted and described. This work can be used to conduct drilling operations in deep exploration wells in fields with difficult mining and geological conditions, in order to conduct drilling operations without complications and accidents.
Keywords: Oil-emulsion humate-lignosulfonate solution, alumocalcium solution, hydrocarbon-based solution, hydrophobization, inhibitor, rheology.
Let's consider the formulation of drilling fluid for two exploration wells drilled at the Northern Goturdepe multi-layer field in order to develop them by dual completion of productive horizons.
By well №147 of the Northern Goturdepe field.
The complex thermogeochemical conditions of drilling well №147 of the Northern Goturdepe area cause, starting from zero and up to the design depth, the need to use drilling fluids with a reduced water yield 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 - +34 °C;
- alumocalcium solutions - A.HKAP-3M - +34 -+92 °C;
- hydrocarbon-based solution - +92 - +104 °C
An oil-emulsion humate-lignosulfonate solution is
used from the beginning of drilling until its effectiveness drops. With the decrease in the effectiveness of the oil-emulsion humate-lignosulfonate solution, the transfer to the inhibited solutions of the ALKAR-3M system and the opening of productive layers on a hydrocarbon-based solution is carried out [1].
Drilling interval 0 - 600 m
When drilling a well from zero to a depth of 600 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 fluid: humates - coal-alkali reagent 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 hydrophobize the solid phase of drilling fluid and improve lubricating properties. To prevent foaming of the solution, a surfactant HT-48 is used. The hydrogen pH of the solution is 8.59.0.
Drilling interval 600 - 2700 m When drilling a well from a depth of 600 m to a depth of 2700 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 fluid and at the same time provides stability and strengthens the walls of the borehole.
Reagents are used as regulators of drilling fluid properties: stabilizers lignosulfonates - ferrochromolig-nosulfonate (FHLC) and KSSB-2, inhibitors - alkaline hydrolysates of Portland cement, thermostabilizers -sodium bichromates (Na2&207) or potassium (K2&207), alkalis - NaOH. The hydrogen pH of the solution is 10-12 [2].
Drilling interval 2700- 3800 m When drilling a well from a depth of 2700 m to a depth of 3800 m, an inhibited heat-resistant solution of ALKAR-3M is used in a zone of moderate temperatures of +92 °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 moderate temperatures.
Drilling interval 3800- 4555 m When drilling a well from a depth of 3800 m to a depth of 4555 m, a hydrocarbon-based solution is used in the zone of elevated temperatures +104 °C, in order to suppress the clays of the lower red-colored thickness and open the 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.
Hydrocarbon-based solutions provide the possibility of drilling unstable, swelling or expanding rocks in the aquatic environment, prevent oil seal formation and tool grabs due to the pressure drop between the well and the formation. They have the best lubricating properties, protect the tool from corrosion. Such solutions have advantages when drilling deep hot wells, salt, anhydrite sediment zones, when drilling small diameter, directional drilling, when drilling formations containing hydrogen sulfide and hydrogen dioxide.
When drilling wells in the areas of Western Turkmenistan, solutions of the "normal" Versadril system have been widely used. This system is a solution based on diesel fuel with a highly emulsified system that withstands high temperatures and at the same time does not lose the stabilizing properties of the solution. This system is successfully used for drilling deep wells.
By well №37 of the Northern Goturdepe field.
The complex thermogeochemical conditions of drilling well №37 of the Northern Goturdepe field, starting from zero and up to the design depth, the need to use drilling fluids with a reduced water yield 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.
An 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 [3].
Drilling interval 0-800m
When drilling a well from zero to a depth of 800 m, an oil-emulsion humate-lignosulfonate solution is used to drill unstable sand-clay rocks of quaternary sediment and stabilize the wellbore.
Stabilizers reagents are used as regulators of the properties of the drilling fluid: humates - coal-alkali reagent 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 hydrophobize the solid phase of drilling fluid and improve lubricating properties. To prevent foaming of the solution, a surfactant HT-48 is used. The hydrogen pH of the solution is 8.5-9.0.
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 [4].
Drilling interval 800- 2800 m 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 fluid and at the same time provides stability and strengthens the walls of the borehole.
Reagents are used as regulators of the properties of drilling fluid: stabilizers lignosulfonates - ferrochro-molignosulfonate (FHLC) and KSSB-2, inhibitors - alkaline hydrolysates of Portland cement, thermostabi-lizers - sodium bichromages (Na2Cr207) or potassium (К2&207), alkalis - NaOH. The hydrogen pH of the solution is 10-12.
For 100 m3 of drilling fluid, it is necessary to add 10-15 tons of oil and 500 - 700 kg of graphite. All these reagents are alternately added to the drilling fluid during one circulation cycle, depending on the volume of the drilling fluid being processed.
The need for further post-treatment of the "weakened" inhibited solution is expedient with an increase in structural and mechanical properties by 10-15%.
Drilling interval 2800-4800 m When drilling a well from a depth of 2800 m to a depth of 4800 m, an inhibited heat-resistant solution of 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.
Drilling interval 4800-5200 m When drilling a well from a depth of 4800 m to a depth of 5200 m, 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.
References:
1. Деряев А.Р., Мамедов Б., Аманов М. Внедрение рецептур буровых растворов для бурения наклонно-направленных и вертикальных скважин. Международная научно-практическая конференция студентов, магистров, аспирантов, соискателей и докторантов. "Рынок и эффективность производства-18", посвященная 30-летию Независимости Республики Казахстан. Сборник трудов. - Кокшетау: 2021. с. 258-261.
2. Деряев А.Р., Гулатаров Х., Мантрова С.В., Рекомендации по буровым растворам для одновременно-раздельной эксплуатации нескольких продуктивных горизонтов на месторождении Северный Готурдепе, Сборник института Нефти и газа, выпуск 8, Ашгабат, Туркменская служба издания 2014.
3. Деряев А.Р., Аманов М., Деряев С.А.. Вскрытие и освоение многопластовых продуктивных горизонтов методом одновременно-раздельной эксплуатации. // Научный журнал Аспирант и соискатель №5 (119), - М: ООО Издательство Спутник +.2020. - с. 23-30.
4. Деряев А.Р., Гулатаров Х., Оразклычев Г., Еседулаев Р. Рекомендации по комплексному освоению метода одновременно-раздельной эксплуатации на месторождениях западной и восточной части Туркменистана / Сборник статей Института нефти и газа, выпуск 11. - Ашгабат: Туркменская Государственная служба печати. 2015.- с.194-202.
DEVELOPMENT OF WELL DESIGNS FOR THEIR DUAL COMPLETION
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.6912986
Abstract
This article describes the development of a well design for dual completion (DC) of multi-layer deposits in order to accelerate the development and increase oil production with the introduction of new technologies and highly efficient equipment. Calculations were made for the development of a well design for DC from the two-year operation of three large horizons, consisting of 7-9 productive layers. As a result, it was determined that the resulting large inflow of oil during the development of these wells proves the success of drilling operations in this area, proving that it is reasonable to choose the right design for dual completion operation of wells.
Keywords: oil and gas phenomenon, conductor, shoe, annular space, borehole, casing string, wellhead, preventer.
The development of the well design begins with the solution of two problems; the determination by calculation of the nominal diameters of the casing strings and the diameters of the rock-breaking tool.
The number of casing strings is determined based on the analysis of the geological section and the location of the well, the presence of areas where drilling is associated with great complications, analysis of changes in the coefficients of anomalous reservoir pressure and absorption indices, as well as accumulated practical experience of well wiring.
The depth of descent of each casing string is specified in such a way that its lower end is in the range of stable monolithic weakly permeable rocks, and that it completely overlaps the intervals of weak rocks in which hydraulic fracturing can occur when opening zones of abnormally high reservoir pressures in the underlying interval [1].
The diameters of the bits, the diameters of the casing columns, the depth of transition from a larger diameter of the well to a smaller one, the depth of descent of the casing columns, the height of the cement mortar behind the casing columns constitute the concept of the well design. The depth of the conductor's descent is determined by the requirement of fastening the upper unstable deposits and isolation of the upper aquifers or absorbing horizons.
When drilling oil and gas fields with high reservoir pressure, it often becomes necessary to install preventers at the mouth of the conductor, then the depth of the installation of the conductor's shoe is calculated from the condition of preventing hydraulic fracturing during the elimination of oil and gas occurrences according to the formula (1).
H = 100XPw + Pwllyegrad Yres.fi.; (1)
The length of the conductor and the height of its cementing are chosen in such a way that it is strong enough and can reliably withstand the forces that may arise when the preventer is closed under the influence of the pressure of productive layers. The possibility of a gas breakthrough from the well through the annular space or through cracks connecting the borehole to the surface should also be excluded.
To select the number of intermediate technical columns and the depth of their descent, a combined graph of changes in reservoir pressure, hydraulic fracturing pressure and hydrostatic pressure of the drilling fluid column is constructed in the coordinates "depth is equivalent to the pressure gradient".
Hydraulic fracturing pressure is determined by the formula (2).
Pfrac. = 0,0083H + 0,66Pres; (2)
In the intervals of occurrence of rocks in which a violation of the borehole zone of the well is possible, where the density of the drilling fluid is selected taking into account the rock pressure, instead of reservoir pressure, rock pressure is applied to the combined graph.
The zones of compatible drilling conditions are the zones of attachment of wells by casing strings, their number corresponds to the number of casing strings.
The compatibility of drilling conditions is understood as such a combination when the created parameters of the technological processes of drilling the underlying interval of the well will not cause complications
