RU2381354C1 - Oil fields development method - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: invention related to oil field development. Method includes dislocation of production and injection wells, pumping a driving fluid through injection wells and product withdrawal through production wells. Additionally define product flooding velocity. Then at the late stage of oil field development, in dependence of the product flooding velocity during production process, gradually transfer production wells, which was flooded at first and which product water content increased 15-20% a year into injection, or execute wells killing. The transfer well of the second group, which product water content increased 5-15% a year into injection, with preliminary pumped in ticked driving medium. Then transfer well of the third group, located closer to production wells constrict rows and oil stagnation zones, which product water content increased 1-5% a year.

EFFECT: oil fields development efficiency increase due to gradual transfer flooded production wells into injection, oil surface efficiency increase, cost cutting due corresponding to water production decrease, pumping it driving medium.

1 ex, 1 dwg

Description

The proposed method relates to the oil industry, in particular to the field of development of oil deposits.

There is a known method of developing an oil field by drilling it with producing and injection wells and then pumping water into injection wells and selecting products from producing wells of all rows to a water content of produced products of up to 80%, and in the last row - up to 98% (Mironov T.P. , Orlov BC Oil recovery from heterogeneous formations during flooding. M: Nedra, 1977, p.233).

The disadvantage of this method is the low coefficient of oil recovery due to the small coverage of the object by drainage (40-70%).

A known method of developing an oil field by drilling a heterogeneous oil field with a system of production and injection wells. In the method, water is injected and each production well is operated to the maximum profitable water cut, followed by their shut-off (M. Surguchev, Secondary and tertiary methods of increasing oil recovery. M .: Nedra, 1985, p. 77).

A significant drawback of this method is that in a heterogeneous object with high viscosity oil, shutting down the wells leads to increased flooding of the nearest producing wells and, as a result, the selection of large volumes of water together with oil and, accordingly, its irrational injection.

The closest in technical essence to the proposed one is a method of developing an oil field, according to which the oil reservoir is drilled with producing and injection wells, well surveys are carried out, the displacing agent is injected and products are taken from the producing wells to the maximum profitable water cut, followed by their shutdown. Upon reaching the maximum water cut of producing wells, polymer solution is pumped into them in the amount of 5-10% of the balance reserves attributable to these wells. At the same time, injection wells are transferred to self-discharge. Production wells located in the area from the side of the watering wells are put into forced operation. Wells located on the opposite side relative to the watered production wells are temporarily stopped. The injection is increased, after which, in injection wells located on the side of the watering wells, injection is reduced and production is increased in production wells. In the area on the opposite side relative to the watered production wells, the injection is increased, reducing the selection with the subsequent commissioning of the watered wells (RF patent No. 2060366, IPC ЕВВ 43/20, publ. BI No. 14, 05/20/1996).

The disadvantage of this method is the low development efficiency due to incomplete production of oil reserves and rapid watering of well products.

The technical task of the proposed method is to increase the efficiency of the development of oil deposits due to the phased transfer to injection of irrigated production wells, an increase in the coverage factor for oil production, saving material costs by reducing water produced with oil along with pumping out the displacing fluid.

This problem is solved by the method of developing oil deposits, including drilling production and injection wells, conducting research in wells, injecting displacing fluid through injection wells and selecting products through production wells, and regulating the operating mode of production wells.

What is new is that they additionally determine the rate of watering of produced products, and at the late stage of development of oil deposits, depending on the rate of watering of produced products during well operation, the first group of waterlogged production wells, whose production watercut increases by 15 per year, is gradually transferred under injection for injection -20%, or carry out their elimination; then the wells of the second group, the water cut of whose production increases by 5-15% per year with preliminary injection of the rim of the thickened displacing agent, then the wells of the third group, located closer to the tightening rows of the producing wells and stagnant zones of oil, the water cut of which increases by 1- 5%.

The conducted patent research on the patent fund of the technical library of the TatNIPIneft Institute showed the absence of identical or equivalent technical solutions in comparison with the claimed method, which allows us to conclude that its criteria are “novelty” and “inventive step”.

The drawing shows a map of the development of oil deposits by the proposed method, where No. 1n - injection well, No. 1-17 - producing wells.

The inventive method is carried out in the following sequence.

An oil field is drilled with a design grid of wells. Displacing fluid is injected into injection well No. 1n and products are taken from production wells No. 1-17. In the process of operation, research is conducted to monitor the operation of injection and production wells: they determine the reservoir properties of the reservoir (permeability, porosity), oil and associated water are sampled, reservoir pressure is measured, the water content of the wells is determined, oil production rates, current oil recovery rates and residual oil reserves.

The injection of displacing fluid significantly affects the performance of the well, especially the increase in reservoir and bottomhole pressures, as well as an increase in oil production and the proportion of water in the produced fluid. As a displacing liquid, water, aqueous solutions of high molecular weight polymers, etc. are used.

Under conditions of a heterogeneous formation structure during injection of displacing fluid into injection wells and selection of products from production wells, an increase in watering of well products occurs depending on the speed of movement of the displacing fluid in the formation. First of all, wells drilled in highly permeable zones of the formation, characterized by the best reservoir properties of rocks (No. 1, 5, 6, 7), are flooded. The time of watering wells (No. 3) located in zones with interbedded high-permeability and clay low-permeability rocks is much longer, since clay interlayers prevent the rapid movement of the displacing fluid through the reservoir, that is, its distribution is uneven.

The longest periods of time are producing wells with a small proportion of water in the production of the well, located closer to the tightening rows of the producing wells (No. 9-14) and stagnant oil zones, as well as drilled in low-permeability zones (No. 2, 4, 8). In this case, the progress of the displacing fluid in the reservoir is slow, and the rate of watering the well’s production is the lowest.

According to the results of studies carried out in the wells, the rate of watering of the produced products is additionally determined, and the producing wells are gradually transferred to injection.

According to the proposed method, depending on the watering rate of the produced products, the producing wells are conventionally divided into three groups: 1) the water cut of the product increases by 15-20% per year; 2) the water cut of well production for the year increases by 5-15%; 3) the water cut of products per year increases by 1-5%.

With a production watering rate in wells (No. 1, 5, 6, 7) of 15-20% per year, production wells are completely flooded for several years of operation and belong to the first group. According to the proposed method, when the water cut of the production of producing wells reaches 94% or more, the wells located in the highly permeable zone are assigned to the first group and transferred to injection (No. 1, 6) in order to involve non-drained oil reserves in the development.

Waterlogged production wells located in dead end zones, or production wells in which the current oil recovery factor has almost reached its final value, are assigned to the first group and are subject to liquidation (No. 5, 7).

According to the results of the research, producing wells are determined whose watering rate corresponds to the second group.

At a rate of production watering in wells of 5-15% per year (No. 3), and at a current watering rate of production of a well not exceeding 50%, in order to prevent premature breakthrough of the displacing fluid in the highly permeable zones of the formation to the producing wells, a thickened displacer is added agent - high molecular weight polymers in the displacing fluid. An aqueous solution of high molecular weight polymers is obtained, which is pumped into the formation. This helps to equalize the front of the advancement of the displacing fluid in the reservoir, which occurs due to an increase in viscosity and a decrease in the displacing mobility of water. As a result, the progress of water in high-permeability reservoirs slows down and low-permeability reservoirs are involved in the development. The above factors contribute to an increase in coverage coefficients and to reduce the unevenness of oil displacement in a heterogeneous formation when an elastic fluid filtration regime is created in it. As a result, less water is taken from the reservoir and higher oil recovery is achieved.

The consumption of high molecular weight polymers does not exceed 0.1% of the displacing fluid. After injection of the fringes of an aqueous solution of high molecular weight polymers with a volume of 5-10% of the amount of oil originally contained in the drainage zone, the producing wells are transferred to the injection fluid.

The tip of an aqueous solution of high molecular weight polymers can be pumped at any stage of development. High oil viscosity (up to 100 mPa · s) and layer-by-layer heterogeneity of the formation are factors that increase the efficiency of the use of polymers. This takes into account data obtained during studies to monitor the operation of injection (flow metering studies) and production wells (reservoir-filtration properties of the formation, water production of wells and reservoir pressure).

With a minimum rate of water cut of produced products of 1-5% per year, producing wells remote from the drainage zone of the injection well, located in low-permeability reservoirs or close to the pulling rows of production wells (No. 9-14), that is, pulling together from different the sides of the displacing liquid, correspond to the third group and continue to work until completely flooded, after which they are transferred under the injection of the displacing liquid according to the proposed method. The injection well No. 1n is stopped because it is located in the washed zone of the formation and the well has fully fulfilled its role in the oil field development system.

Practical example

The implementation of this method, consider the example of an oil reservoir. The deposit is drilled with a rare grid of vertical wells with a distance between the wells of 350 m, their arrangement and operation are carried out. Based on the results of geophysical and field studies conducted in the wells, the reservoir properties of the reservoir are determined, and reservoir pressure is measured. The balance reserves of the deposit site are 472 thousand tons. The average permeability of the highly permeable zone (No. 1, 5, 6, 7) is 0.450 μm ² , and the watering rate is 18% per year, of the low permeability zone (No. 2, 4, 8), respectively, 0.076 μm ² and 9% per year, and zones in the area of well No. 3, respectively - 0.102 μm ² and 4% per year.

As a displacing liquid, water is used. Water is injected into an injection well (No. 1n) with a pressure of 12 MPa at the wellhead and oil is extracted from production wells. They measure oil production, produced water and injected fluid. After 4.5 years of operation, production wells No. 5 and No. 7 were irrigated to 97 and 95%, respectively. The specific recoverable oil reserves for each well were selected at 35-40%, that is, the current oil recovery factor (CIN) has almost reached its final value. Production wells are located in a dead end zone, therefore, are subject to liquidation.

Production wells No. 1 and 6, located in a highly permeable zone, were flooded to 94 and 98% each in 5.4 years. The rate of watering wells amounted to 20.9 and 21.8% per year, respectively, that is, the wells belong to the first group. Reservoir pressure decreased to 10.2 MPa. The presence of cost-effective residual oil reserves in the surrounding producing wells (85 and 94 thousand tons, respectively) and the creation of a reservoir pressure maintenance system (PPM) in the reservoirs are the determining factors for transferring wells No. 1 and 6 to injection, contributing to the most complete development of reserves in the reservoirs.

Production well No. 3, after 9 years of operation, was flooded to 48%. Well watering rate was 5.3% per year, that is, the well belongs to the second group. The reservoir is heterogeneous in its reservoir properties. The reservoir pressure in the reservoir area decreased to 9.5 MPa. Analysis of the operation of injection wells (No. 1 and 6) showed that the effect of the injected fluid on part of the reservoir (No. 2, 4, 12, 13, 14) is insufficient, and the question arose of its optimization.

In order to level the front of the displacement fluid advancement in the reservoir and to involve low-permeability reservoirs in the development of the reservoir with low reservoir pressure, the displacement fluid was pumped into well No. 3 and 0.05% polyacrylamide (PAA) was added. The volume of the rim of the aqueous PAA solution was 10% of the amount of oil originally contained in the formation. Further work of the well as an injection was carried out at injection pressures providing reservoir pressure close to the initial (11.2-10.8 MPa). An increase in the oil recovery ratio over the reservoir area was 5%.

Production wells No. 2, 4 are located in a grid step at a distance of 350 m from the tightening row of production wells, well No. 8 - in the zone with low permeability reservoirs. Well watering rate was 3.9, 3.5, and 3.1% per year, respectively, that is, wells belong to the third group. The residual oil reserves of the surrounding wells are 62 and 78 thousand tons. Slow advancement of the injected fluid through the formation towards production wells affects the rate of water cut in the production of the well. The reservoir pressure is maintained at a level close to the initial (11.0-10.6 MPa). After 25, 28 and 30 years of operation, the wells were flooded to 97.5, respectively; 98 and 94% and were transferred under injection of displacing fluid. The injection well 1n is stopped, since it is located in the completely flooded zone of the formation and has fulfilled its task in the development system of the oil reservoir under consideration.

The use of data on the rate of waterlogging of well products allows the proposed method to be implemented, provides an increase in the efficiency of oil field development due to the phased transfer to injection of irrigated production wells, helps to increase the coverage factors and reduce the uneven displacement of oil in an inhomogeneous formation while creating an elastic fluid filtration regime in it. As a result, less water is taken from the reservoir and higher oil recovery is achieved.

Claims (1)

The method of developing oil deposits, including the placement of production and injection wells, injection of displacing fluid through injection and selection of products through production wells, characterized in that they additionally determine the rate of watering of the produced products and at the late stage of development of oil deposits depending on the rate of watering of the produced products during operation wells are gradually transferred under injection to the first waterlogged producing wells of the first group, the water cut of the product which increase by 15-20% per year, or liquidate them, then the wells of the second group, the water cut of which increases by 5-15% per year, with preliminary injection of the rim of the thickened displacing agent, then the wells of the third group, located closer to tightening rows of producing wells and stagnant zones of oil, the water cut of which increases by 1-5% per year.

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