RU2151860C1 - Method for development of oil pool with bottom water - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: when developing oil pool with bottom water, working agent is injected through injection wells, product is taken out of productive wells, and system controlling pressure between oil- and water-bearing parts of bed is created. Formation pressure is maintained at the level of values ensuring establishment of static level in wellhead zone of productive wells. For production of oil, those productive wells having elevated hypsometric formation marks are selected. Pressure fluid is emptied from holes of these wells and the latter are filled with oil of the same pool. Upper boundaries of productive formation in these wells are reuncovered in oil medium of wells to form perforated holes with depths exceeding thickness of mudded zone. Production of oil is periodical using well hole from well head level as tank for settling and accumulation of oil. EFFECT: accelerated oil production.

Description

 The invention relates to the field of development of oil deposits and may find application in the operation of deposits with bottom water.

 A known method for the development of oil deposits, lined with bottom water, which consists in changing the flow of fluid in the reservoir and the selection of products from producing wells [1].

 The disadvantages of the method are the low oil recovery coefficient and a large selection of associated water caused by the formation of bottom water cones during operation of the wells.

 There is a method of developing an oil reservoir with bottom water, including drilling production and injection wells, selecting products from production wells, creating a system for monitoring and regulating the pressure between the oil and aquifer parts of the reservoir [2].

 A common disadvantage of the known methods is their low efficiency. This is explained by the fact that during the operation of the producing well, oil is not displaced from the roof of the formation, because forces pushing oil from the reservoir into the well are much less hydrodynamic. The filtration resistance of the reservoir for oil exceeds the filtration resistance for water. Water flows from the water-saturated (washed) part of the formation into the well without displacing oil. This reduces reservoir coverage by water flooding and leads to the withdrawal of large volumes of water.

 Closest to the invention, the technical essence is a method for developing a water-oil deposit, which includes injecting a working agent through injection wells, taking products through production wells, creating a system for monitoring and regulating pressure between the oil and aquifer parts of the reservoir, maintaining pressure in the reservoir at a level that provides the establishment of a static level in the estuarine well, and the periodic selection of oil [3].

 The disadvantage of this method is the low rate of oil selection due to a decrease in the efficiency of the method over time. This is explained by the fact that the working oil-saturated thickness of the roofing part of the formation, giving off oil, becomes insignificant due to imperfection of opening the formation, oriented to a highly permeable reservoir, and low hypsometric marks of the formation in the wells.

 The invention solves the problem of increasing the rate of oil extraction by increasing the working oil-saturated thickness, giving oil.

 The problem is solved in that in a method for developing a reservoir of oil with bottom water, which includes injecting a working agent through injection wells, taking products through production wells, creating a system for monitoring and regulating the pressure between the oil and aquifer parts of the reservoir, maintaining the pressure in the reservoir at a level of, providing the establishment of a static level in the estuarine zone of production wells, and periodic oil selection, according to the invention, production wells having increased gypsum are selected for oil selection metric marks of the formation, while in these wells, the roofing part of the productive formation is secondly opened in the oil medium with the formation of perforation holes with a depth exceeding the thickness of the columnar zone.

The features of the invention are:
1. injection of a working agent through injection wells,
2. selection of products through production wells;
3. creating a system for monitoring and regulating pressure between the oil and aquifer parts of the reservoir;
4. maintaining the pressure in the reservoir at a level that ensures the establishment of a static level in the estuary zone of producing wells;
5. the choice of oil extraction wells that have elevated hypsometric marks of the reservoir,
6. secondary opening of the roofing of the reservoir in these wells;
7. the same in the oil environment;
8. the same with the formation of perforation holes with a depth exceeding the thickness of the colonized zone;
9. The selection of oil from these wells periodically.

 Signs 1-4, 9 are common with the prototype, signs 5-8 are the salient features of the invention.

SUMMARY OF THE INVENTION
When developing an oil reservoir at a late stage, the rate of production of oil reserves becomes very low. The proposed method solves the problem of increasing the rate of oil extraction.

 The method is carried out in the following sequence.

 The reservoir area having a waterlogged formation with residual oil reserves concentrated in the roofing part of the structure is operated by producing and injection wells. The site is operated at reservoir pressure close to the original, i.e. equal to the hydrodynamic, mechanized method with the descent of the deep pump into the wellhead.

 In the process of drilling and operating wells, wells are examined, the parameters of the formation and the fluids saturating them are determined. Measure formation pressure. Well production samples are taken. The method is applicable when the specific gravity of the oil is less than the specific gravity of the bottom water.

 When selecting products using gravity, bottom water, displacing oil to the upper perforations, prevents oil from entering the well. Since the initial perforation was intended for highly permeable reservoirs and has a shallow depth with an insignificant density of holes per linear meter, and the roof part of the reservoir, as a rule, with deteriorated reservoir properties, remains imperfect in opening degree, due to the large filtration resistances of the bottom-hole zone in the dome part of the reservoir and a small working oil-saturated part of the reservoir, oil enters in small quantities and at an insignificant speed into the well. The well selects products with a low pace of selection. The process of exploitation of the reservoir becomes ineffective with a significant residual oil-saturated thickness of the reservoir.

 According to the results of the study of wells begin to implement the method.

 The well is stopped and the geological and field types of research determine the residual oil-saturated thickness of the reservoir and the degree of perfection of opening the bottom-hole zone of the well. For oil selection, wells with increased hypsometric marks, that is, located in elevated sections of the reservoir, are selected. A structural map is constructed along the roof of the productive horizon. The choice of wells with elevated hypsometric marks is due to the fact that oil will tend to occupy the upper part of the reservoir structure due to gravitational forces. In the same wells, additional perforation of the roofing part of the formation is performed. For this, a perforator is lowered into the well. Previously, underground equipment (pump) for production is dismantled from the well, the filling fluid is removed from the wellbore and filled with oil of the same reservoir. The choice of the type of perforator depends on the design of the wells, oil-saturated thickness and reservoir characteristics of the roof of the formation. With a small oil-saturated thickness and a weak cement stone behind the column, additional perforation is performed by drilling perforators. With a significant thickness of the columns and low reservoir characteristics of the formation, an in-depth secondary opening is performed by cumulative perforators. The power of the charges is chosen so that the depth of the holes exceeds the thickness of the zoned zone. As a rule, these are holes with a depth of 500 - 850 mm. Since the column is filled with oil, a decrease in the phase permeability of the well oil does not occur. The well is put into operation with the selection of oil from the estuary zone. If the well overflows, then the injection of water into the injection wells is limited. At a low static level, increase injection volumes. If there is a connection with the marginal region and the energy characteristic of the formation allows you to maintain a static level in the wellhead, then there is no need to control the injection volumes. A well with a low hypsometric mark and a small oil-saturated thickness can be converted to water injection and the residual oil from the zone of this well should be displaced into the zones of the wells with elevated hypsometric marks.

 Having established a static level in the wellhead zone of the well, it is stopped for gravitational redistribution of phases in the well-formation system.

 Due to the greater specific gravity, bottom water located in the wellbore and in the cone will tend to occupy the lower part, and oil will “float” and advance to the selection zone. The flow of water into the bottom of the formation creates a force that squeezes the oil into the well.

 Having a lower specific gravity, oil in the well also floats due to gravitational forces and occupies its upper part, i.e. I bring it to the mouth. The establishment of a static level in the immediate vicinity of the mouth is associated with greater potential energy for the gravitational separation of oil and water. Using the wellbore from the mouth as a reservoir for sludge and oil accumulation allows you to select anhydrous oil with low energy costs for its pumping and use non-metal-intensive equipment for production.

 Since wells with increased hypsometric marks were selected for oil selection, where oil is going from the reservoir, and deep perforation was made, which allows to increase the discovered oil-saturated thickness and reduce the filtration resistance of the bottom-hole zone, the well production rate increases. The time required for the accumulation of oil is reduced and depends on the reservoir and physico-chemical properties of the reservoir and oils, the ratio of the specific gravities of oil and water. The specific amount of oil accumulation time is determined in the field. The well is equipped with a sensor for measuring the oil-water section in the well. After the oil-water section in the well reaches a certain level, oil is pumped out until water appears. Plantar water enters the roof of the formation to the upper perforations and displaces oil into the producing well. Waterflood coverage increases with increasing oil recovery rates.

 An example of a specific implementation.

The area of oil deposits with bottom water is exploited by three producing wells. Products are selected from a carbonate formation with a total thickness of 45 m, including oil saturated 15 m, water saturated 30 m. According to the well survey data, it was revealed that the oil deposit is confined to the anticline with marks of the roof of the beds in the well N 1 - 900 m, N 2 - 950 m, N 3 - 900 m. The deposit has an active aquifer , therefore, it is developed on a natural water-pressure mode. In the process of drilling wells, core samples are taken. According to the results of the core study, the formation parameters are determined by which the oil reserves are calculated. 640 thousand tons of balance reserves are concentrated in the area of these wells. Produce oil selection. Oil has a low gas content. The specific gravity of oil is 850 kg / m ³ .

 A deposit is developed without maintaining reservoir pressure in a mechanized way. The static level is at a level of 80-100 m from the wellhead. Well survey results show that the remaining reserves are confined to the roofing part of the formation and most of them are associated with low-amplitude structure uplifts. A study by the locator of the couplings shows that the oil-saturated thickness not opened by perforation in well N 1 is 4 m, N 2 is 0.5 m and N 3 is 5 m. The permeability of the roof of the formation is 2 times lower than the bottom.

 To connect to the active development of the roofing of the formation using gravity in the well-formation system, the well is stopped. Pumping equipment is raised to the surface. The reservoir is crushed by pumping oil into it. The PK-105 puncher is lowered and a lumbago of the roof part of the formation with a density of 30 holes per meter is produced. The power of the charges allowed making holes with a depth of 500 - 850 mm. Wells N 1 and N 3 are launched for oil extraction, and well N 2 is injected. Wells N 1 and N 2 are equipped with a controller to determine the rate of gravity redistribution of oil and water and its accumulation in the well. Measurements are taken to beat the oil-water section. For twenty days in a well N 1, a column of oil 250 m high was installed, N 3 - 300 m high, which is three times faster before the events. Based on the results of the study, the depth of the descent of the pump is determined and the well operation program for pumping anhydrous oil is established. A pump is lowered into the well above the oil-water section. Produce oil selection. Annual oil production increased from 125 tons to 3,000 tons. The oil production rate increased from 0.05 to 0.88% of the balance reserves.

 Application of the proposed method will increase the rate of oil selection.

Sources of information
1. M. L. Surguchev. Secondary and tertiary methods of increasing oil recovery. - M .: Nedra, 1985, - p. 85.

 2. "Geology and development of the largest and unique oil and gas fields in Russia." Abdulmazitov R.G. et al. - M.: VNIIOENG, 1996, v. 1, p. 67.

 3. RF patent N 2138625, cl. E 21 B 43/20, published. 09/27/99, in BI N 27, 1999 - a prototype.

Claims (1)

 A method of developing a reservoir of oil with bottom water, including pumping a working agent through injection wells, taking oil through production wells, creating a system for monitoring and regulating the pressure between the oil and aquifer parts of the reservoir, maintaining pressure in the reservoir at a level that ensures the establishment of a static level in the wellhead the zone of production wells, and periodic oil selection, characterized in that for the selection of oil choose production wells having elevated hypsometric marks of the reservoir, from the wells of these wells remove the filling fluid, fill them with oil of the same reservoir, and in the oil medium of these wells reopen the roofing of the reservoir with the formation of perforations with a depth exceeding the thickness of the sealed zone, while using the wellbore from the wellhead as a reservoir for sludge and oil accumulation.