RU2189442C2 - Method of cleaning the producing formation bottom-hole zone - Google Patents

Abstract

FIELD: development of oil and gas deposits by wells; applicable in cleaning of bottom-hole zone of producing formation after well drilling. SUBSTANCE: method includes successive injection of selected portions of chemical reagents into bottom-hole formation zone. In so doing, prior to treatment of bottom-hole formation zone and after supply of every chemical reagent, zone supersaturated with gas built up in bottom-hole formation zone by gas injection at pressure exceeding formation pressure. In this case, gas is supplied to bottom-hole zone at minimal flow rate, and supersaturated zone is built up with radius exceeding that of contaminated part of bottom-hole zone. After leaving the well to stand for time required for performance of reaction of chemical agents with producing well rocks and contents of porous medium, bottom-hole formation zone is cleaned from reaction products by putting well into operation. EFFECT: higher efficiency of cleaning of bottom-hole zone of producing formation from filtrate of drilling mud and reaction products. 1 ex

Description

 The invention relates to the field of downhole development of oil and gas fields and can be used to clean the borehole zone of a productive formation after drilling a well.

 There is a known method of treating a formation, which consists in removing the mud filtrate from the bottomhole zone into the depth of the reservoir by injecting reverse oil emulsion into the reservoir in an amount equal to 3-5 volumes of infiltrated filtrate, while the viscosity of the fluid as it is injected changes from the viscosity of the mud to the viscosity reservoir oil / 1 /.

 The disadvantage of this method is the impossibility of using it to clean the near-wellbore zone of low-permeable productive formations, since in this case, to "bury" the mud filtrate in the productive formation, it is necessary to create large repressions that are undesirable due to a possible violation of the tightness of the cement ring of the production casing or the casing itself.

 A known method of cleaning the borehole zone by chemical exposure to the formation, including determining the geological, physico-chemical properties of the rocks of the reservoir and formation fluids, selecting chemical agents (based on determining the properties of the rocks and formation fluids), pumping them through tubing into the borehole part productive formation, holding the well for the time of the reaction of chemical reagents with the rocks of the productive formation and formation fluids and cleaning the bottom of the formation from reaction products during uske work well in / 2 /.

 The disadvantages of this method include the fact that during its implementation it may be difficult to clean the treated zone of the formation from the reaction products of the applied chemicals with rocks and formation fluids, especially in low-productivity formations, since when the well is put into operation, the created velocities of formation fluids can be insufficient for removal of reaction products from the borehole zone of the formation.

 Closest to the described method is a method of intensifying the influx of hydrocarbons to the well, including determining the geological, physicochemical properties of the rocks of the reservoir and formation fluids, lowering the tubing string into the well and sequentially pumping selected portions of chemical reagents into the borehole portion of the formation, before processing the borehole part of the formation and after supplying each chemical reagent by pumping gas, a supersaturated gas is created in the borehole part of the formation ohm zone of increased pressure exceeding the reservoir pressure. After holding the well for the duration of the reactions of chemical reagents with the rocks of the productive formation and formation fluids, the bottom-hole part of the formation is cleaned of reaction products by putting the well into operation / 3 /.

 The disadvantages of this method of cleaning the near-wellbore zone of the reservoir and intensifying the flow of hydrocarbons to the well include the fact that when it is implemented at unlimited rates of gas injection, the filtrate of the drilling fluid may be pushed into the depth of the reservoir, which can reduce the efficiency of its cleaning.

 The objective of the invention is to increase the efficiency of cleaning the near-wellbore zone of the reservoir from mud filtrate and reaction products.

 This object is achieved by the fact that when implementing the method of cleaning the borehole zone of a productive formation, including treating the borehole zone with chemical reagents, creating a gas-saturated zone of increased pressure exceeding the reservoir pressure by pumping gas before and after each portion of the chemical reagent, holding the well for the duration of the chemical reaction reagents with the rocks of the reservoir and the contents of the porous medium and the launch of the well into operation, according to the invention, gas is supplied to the wells zone with a minimum flow rate, and a gas-saturated zone is created with a radius greater than the radius of the contaminated part of the near-wellbore zone.

 The invention consists in the following.

 After drilling oil and gas wells during their development, there is a need to clean the borehole zone of the reservoir from the mud filtrate, and sometimes to improve the initially low filtration parameters of the reservoir. According to the described method, in order to restore and improve the filtration parameters of the well, the first portion of gas is initially pumped into it. Gas is pumped at a minimum flow rate, therefore, when it enters the borehole zone of the reservoir, uniformly across the entire thickness of the reservoir it partially displaces the mud filtrate deep into the reservoir from the bottom of the well, creating a saturation of the borehole zone with gas sufficient for gas movement (about 10%). At the same time, gas is supplied in an amount sufficient to saturate it with a zone whose radius exceeds the radius of the contaminated zone (mud filtrate saturated). Thus, in the near-well zone, filtration channels are created to the reservoir fluid of the reservoir and a gas buffer outside the contaminated zone. After a portion of gas, the first portion of a chemical reagent is fed into the well. This reagent is intended primarily for dissolving sludge precipitated from the drilling fluid, or increase its mobility (for example surfactants). Following the first portion of the chemical reagent, a second portion of gas is fed into the well, which displaces the previously pumped portions of gas and chemical reagent, as well as the mud filtrate from the bottom of the well, ensuring their mixing and the dissolution of the mud sediment. In addition, the gas of the second portion dissolves in the reaction products of the first portion of the chemical reagent and the remainder of the reservoir fluid, reducing the viscosity of the resulting mixture. Then, a second portion of a chemical reagent is fed into the well and squeezed into the formation, for example, for reacting with the rocks of the productive formation and improving its filtration parameters. This portion gets into the porous medium of the near-wellbore zone, purified from the mud filtrate, therefore the effect of the chemical treatment of the producing formation increases. Sequentially pumped portions of chemicals and gas (the number of which depends on the problem being solved) with a pressure in excess of the reservoir, allow to dissolve and (or) remove substances that worsen the filtration parameters of the near-wellbore zone and reduce the viscosity of the resulting fluid mixture. The injection of portions of gas with minimal costs allows more even treatment coverage of the borehole zone, preventing breakthrough of injected gas and chemicals in the most permeable interlayers. After holding the well for the duration of the reaction of chemicals with the sediment of the mud filtrate and the rocks of the reservoir, the well is put into operation. Since the last portion supplied to the well is a portion of gas, when starting a well, it is possible to create a wide range of regulated depressions on the formation, ensuring effective cleaning of the wellbore zone from reaction products and preservation of the wellbore zone from destruction. At the same time, the cleaning efficiency is further increased due to the movement of gas portions to the bottom of the well located in the borehole part of the reservoir under pressure, as well as the formation fluid, the connection of the borehole space with which is provided by the injection of gas portions.

An example implementation of the method
In a well with a depth of H = 2000 m, which uncovered a reservoir with a thickness of h = 10 m, composed of carbonate rocks, it is necessary to intensify the inflow by cleaning the bottomhole zone from the mud filtrate and increase the porosity of the reservoir of the bottomhole zone of the reservoir. We use surfactants (for example, OP-10) as a reagent for cleaning the bottom-hole zone, and a solution of hydrochloric acid to increase the porosity of the collector. The initial porosity of the formation m = 0.1, the radius of the zone contaminated with the mud filtrate R _b = 3 m, the radius of the hydrochloric acid treatment of the bottom-hole zone of the formation R _k = 5 m, the reservoir pressure R _pl = 20 MPa, reservoir temperature T _pl = 340 K, tubing inner diameter D _NTK = 0.062 m.

- объем порции ПАВ; приравниваем объем этой порции объему одной трети порового пространства обрабатываемой зоны (R_б=3 м):
V×1 = 0,33πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{б}}$ hm≅9,3 м³;
- объем второй порции газа (при нормальных условиях); считаем, что при закачивании этой порции газ заполняет 80% объема порового пространства загрязненной зоны (остаточная насыщенность порового пространства неподвижной влагой - 20%):
Г₂ = 0,8πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{б}}$ hm(P_плT_o/P_oT_плz)≅4034 м³;
- объем раствора соляной кислоты; насыщенность раствором соляной кислоты порового пространства в обрабатываемой зоне составляет 20%:
V_к = 0,2πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{к}}$ hm = 15,7 м³;
- объем третьей порции газа при нормальных условиях (с учетом продавливания кислоты в пласт на глубину R_Г3 = 1 м и заполнения колонны НКТ, приравнивая средние значения давления и температуры пластовым параметрам):
Г₃ = (πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{г3}}$ hm+πHD $\genfrac{}{}{0ex}{}{\text{2}}{\text{нкт}}$ /4)(P_плT_o/P_oT_плz) = 1637 м³.
Последовательно закачиваем в скважину и продавливаем в призабойную зону продуктивного пласта расчетные порции газа и реагентов по технологии, описанной выше. После выдержки пласта на время реакции соляной кислоты с горными породами скважина запускается в работу.We determine:
- the volume of the first portion of gas (under normal conditions - P ₀ and T ₀ ); this portion of gas creates a gas saturation of the contaminated zone (R _b = 3 m) equal to 10% and a gas-saturated buffer zone to a depth of 2 m (3 to 5 m from the bottom of the well), then the volume of the portion of gas will be:

- portion size of surfactant; we equate the volume of this portion with the volume of one third of the pore space of the treated zone (R _b = 3 m):
V × 1 = 0.33πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{b}}$ hm≅9.3 m ³ ;
- the volume of the second portion of gas (under normal conditions); we believe that when this portion is pumped in, gas fills 80% of the pore space of the contaminated zone (residual saturation of the pore space with still moisture is 20%):
G ₂ = 0.8πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{b}}$ hm (P _pl T _o / P _o T _pl z) ≅ 4034 m ³ ;
- volume of hydrochloric acid solution; the saturation with a solution of hydrochloric acid in the pore space in the treated zone is 20%:
V _k = 0.2πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{to}}$ hm = 15.7 m ³ ;
- the volume of the third portion of gas under normal conditions (taking into account the forcing of the acid into the formation to a depth of R _Г3 = 1 m and filling of the tubing string, equating the average pressure and temperature to the formation parameters):
G ₃ = (πR $\genfrac{}{}{0ex}{}{\text{2}}{\text{g3}}$ hm + πHD $\genfrac{}{}{0ex}{}{\text{2}}{\text{tubing}}$ / 4) (P _pl T _o / P _o T _pl z) = 1637 m ³ .
Subsequently, we pump into the well and push the calculated portions of gas and reagents into the bottomhole zone of the productive formation using the technology described above. After holding the formation during the reaction of hydrochloric acid with rocks, the well starts up.

 Using this method can successfully solve the issues of intensification of the influx of hydrocarbons to the well due to the high efficiency of cleaning the near-wellbore zone from the mud filtrate, from the reaction products of the chemicals used when the well is put into operation after intensification work.

Literature
1. RF patent 1063988, cl. E 21 B 43/25, priority 02.03.1982.

 2. Mineev B.P., Sidorov N.A. A practical guide to testing wells. M .: Nedra, 1981, p. 163-183.

 3. RF patent 2127806, cl. E 21 B 43/27, priority 09.04.1998.4

Claims (1)

 A method of cleaning the near-wellbore zone of a reservoir, including treating the near-wellbore zone with chemical reagents, creating a gas-saturated zone of increased pressure exceeding the reservoir pressure by pumping gas before and after each portion of the chemical reagent, holding the well for the duration of the reaction of chemical reagents with the rocks of the reservoir and contents of a porous medium and the launch of a well into operation, characterized in that the gas is supplied to the near-wellbore zone with a minimum flow rate, while the gas is saturated with gas Well create a radius of more than the radius of the contaminated part of the borehole zone.