EA025574B1 - Method for development of petroleum and gas condensate pre-salt and post-salt deposits - Google Patents

Abstract

The method is based on the possibility of utilizing hydrocarbon crossflows from productive pre-salt deposits to post-salt deposits using technical well-drilling means; at each local pre-salt structure with an above-lying post-salt reservoir, drilling of a process pre-salt well in the dome of the pre-salt reservoir is performed. When doing this, the possibility of adjustable vertical supply of hydrocarbons from the pre-salt deposits to the post-salt reservoir is provided by installing in the well a technical string, the perforated section of which is arranged opposite to the productive horizon of the post-salt reservoir. Induction of hydrocarbon materials inflow from the pre-salt deposits is performed with the well mouth closed, through the perforated section of the string, directly to the post-salt deposit, and after saturation of that deposit, hydrocarbon materials are extracted by the free-flow production method through post-salt producing wells. Then, for maintaining the operating reservoir pressure higher than the saturation pressure, and for increasing the ratio of hydrocarbons extraction to the post-salt reservoir through the perforated section of the technical string functioning as a fill-in well, associated petroleum gas is pumped into productive horizons of the post-salt complex. As the reservoir pressure decreases, nitrogen is pumped in, a minimum level of depression on the pre-salt reservoir is reached, and complete extraction of geological reserves of hydrocarbon materials through producing wells of the post-salt reservoir is provided. The technical result is attained also by that hydrocarbons extraction, for eliminating contamination of the bottom-hole formation zone and ensuring maximum possible oil flow rate from the pre-salt well, is performed during open-hole operation of the pre-salt well, and the produced oil is directed to the post-salt reservoir that performs the function of a temporary subsurface storage facility for hydrocarbon materials. The use of the method will allow reduction in the amount of construction of ultra-deep pre-salt wells at each deposit; a lower prime cost of oil produced; smooth adjustment of pre-salt oil volumes flowing to post-salt deposits, and adjustment of pressures and flow rates of producing post-salt wells.

Description

The invention relates to the oil industry and can be used in the development of subsalt deposits of oil and gas condensate, as well as newly discovered, as well as fully or partially recognized oil, gas and gas condensate suprasalt deposits.

The need and practical importance of creating an effective technology for the development of supra-salt and sub-salt deposits, containing, according to various estimates, oil and gas condensate reserves that exceed all the geological reserves of all known deposits that have already been discovered at present, is very great.

The massive development of subsalt deposits is restrained by the large depths of oil, gas and gas condensate and abnormally high formation pressures and temperatures. Intervals of subsalt productive complexes occurring in the depth range from 2700 to 5500 m or more. The excess of reservoir pressure over hydrostatic in subsalt wells reaches 1.95 times, and the temperature in the deposits is 110-120 ° C, which corresponds to a geothermal gradient in the intervals from 0-5600 m of sedimentary cover 2.20 ° / 100 m (see Internet: Caspian oil and gas field , materials from Wikipedia, the free encyclopedia).

Although the above data determine the complexity of drilling, development and the high cost of constructing deep subsalt wells, it is also noted that drilling organizations have practically solved the main technical and technological problems of drilling subsalt deposits. So, in an article by IB Dalyana Peculiarities of tectonics of subsalt complexes of the eastern margin of the Caspian Basin in connection with oil and gas potential (Journal of Geology of Oil and Gas, No. 6, 1996) noted that about 500 wells were drilled by oil exploration expeditions for subsalt deposits to a depth of 6,200 m. Moreover, Kik-Chli presented on the Internet, information about drilling in Uzbekistan for subsalt deposits with a horizontal section of the well in the salt layer up to 1000 m. The same company drilled 10 deep horizontal wells. The deepest horizontal well vertically is 6040.67 m, the longest well length along the bore is 6699 m, bottomhole pressure is 140 MPA at bottomhole temperature 145 ° C, oil reservoir depth is 5700-6500 m. In the known detection method oil and gas condensate deposits in subsalt deposits (RF patent No. 2073258, MPZh O01U 9/00, 1997) exploratory wells are drilled in areas of sharp reduction in the capacity of subsalt anhydrites. At the same time, the possibility of using overlying suprasalt productive formations is not taken into account. The development of subsalt and supra-salt oil deposits is constrained by the lack of new effective methods for developing fields and methods of organizing industrial oil production and, in general, the lack of a methodology for the joint development of subsalt and suprasalt deposits. Currently, all the deposits in the supersalt complex are already at the last stage of oil production, which is carried out by the old mechanized method. Heavy oil deposits in the fields are usually developed with heat and steam, and the development of oil and gas condensate deposits of subsalt deposits is carried out in a natural mode of depletion (see the Caspian oil and gas province Mountain Encyclopedia under the editorship of EA Kozlovsky, Almaty, 1990).

Despite the large volume of drilling exploratory and exploratory wells for subsalt deposits, the problems of the normal call of hydrocarbon inflows (HC) from subsalt wells are still not sufficiently solved. At the same time, only in single subsalt wells did the normal production rates reach significant values, while at open fountains, production rates up to 1000 m / day and more were stably observed. The reason for this phenomenon are two circumstances. Firstly, in contrast to modern technologies, in all cases of sudden open well flowing, there is a decrease in back pressure on the productive horizon only due to a gradual decrease in the specific gravity of the wash fluid column, i.e. the influx of hydrocarbons from the reservoir into the wellbore always occurs with a gradual decrease in back pressure on the opened production horizon. Secondly, from the beginning of the flowing of the well until the start of the killing of the fountain there is no back pressure on the working formation. Therefore, if the creation of new technologies for the development of subsalt deposits will solve these problems, i.e. the hydrocarbon influx will be called smoothly and throughout the entire period of the well’s operation the flowing flow will be provided with the exception of the need to create backpressure to the productive horizon, this development method will be most effective. That is why, when developing technologies for the normal opening of productive horizons, methods for inflow calls and oil production technology during the operation of the well and the entire field, ensuring a smooth call for oil inflows and creating conditions for the lack of backpressure on the productive horizons are the main unsolved problems that hamper the mass development of subsalt deposits. It should be borne in mind that the solution to these problems is practically possible, and this is clearly proved by the large flow rates of wells, which are achieved with open fountains.

Geological studies conducted in the processing of primary information on drilling and geophysical studies of wells drilled for subsalt and suprasalt deposits,

- 1 025574 revealed certain relationships between the underlying subsalt and overlying suprasalt productive formations. In the formation of hydrocarbon deposits in suprasalt deposits, the decisive role is played not only by the sedimentary deposits own potential, but also by the supply of hydrocarbons from the underlying sediments. According to the results of geochemical studies carried out using the latest research methods such as high-voltage resonance, the study of carbon isotopic composition, etc., the genetic unity of oil from subsalt and suprasalt deposits is proved, the formation of which is explained by the vertical flow of hydrocarbons from subsalt deposits. Paleophytological studies confirm the existence of vertical flows of oil in subsalt deposits and from subsalt to suprasalt. At the same time, the similarity of subsalt and supersalt oils is noted, based on their chemical composition in the stripped portion of the oils and according to IR spectrometry and carbon isotopic composition (see the article by Yu.A. Ivanov, Prospects for oil and gas potential of the pre-salt and subsalt complexes of the Caspian depression in the journal Geology of Oil and gas, No. 7, 1988).

The theoretical possibility of using hydrocarbon overflow from productive subsalt deposits to overlying developed suprasalt deposits was the basis for the selection of this fact as a prototype of the invention, the implementation of which becomes possible using well-known existing technical means.

The objective of the invention is to provide an effective method for the development of oil and gas condensate subsalt and supersalt deposits, ensuring the supply of hydrocarbons from underlying productive subsalt deposits with abnormally high reservoir pressures and temperatures to the overlying layers of supersalt deposits in order to produce oil and gas condensate through the production wells of the supersalt complex under normal conditions corresponding to pressures slightly exceeding the hydrostatic pressure, which It would ensure the fountain production of hydrocarbons of both subsalt and shallow suprasalt horizons at normal temperature and pressure at the wellheads.

The technical results of the invention are as follows:

reduction in the construction of super-deep subsalt wells at each field;

reduction in the cost of produced oil;

smooth regulation of volumes of inflow of saline oil to suprasalt deposits, as well as regulation of pressures and production rates of suprasalt wells.

The task and technical results are achieved by the fact that in the method of developing oil and gas condensate subsalt and supra-salt deposits, based on the possibility of using hydrocarbon flows from productive subsalt deposits to supra-salt deposits using technical means for drilling wells, on each local subsalt structure located above it with a pre-salt deposit, a technological subsalt well is drilled in the dome of an over-salt deposit. At the same time, they provide the possibility of a controlled vertical supply of hydrocarbons from sub-salt deposits to the suprasalt deposit due to the installation of a technical column in the well, the perforated section of which is located opposite the productive horizon of the suprasalt deposit. The inflow of hydrocarbon feed from subsalt deposits is called up when the wellhead is closed through the perforated section of the column directly to the suprasalt deposit and, after its saturation, the hydrocarbon feed is extracted in a fountain way through the suprasalt production wells. Then, in order to maintain the working reservoir pressure above the saturation pressure and increase the coefficient of hydrocarbon extraction into the suprasalt reservoir, associated petroleum gas is pumped into the productive horizons of the suprasalt complex through the perforated section of the technical column acting as an injection well. With a decrease in reservoir pressure, nitrogen is pumped in, a minimum level of depression on the subsalt reservoir is achieved, and the geological reserves of hydrocarbons of the subsalt reservoir are fully extracted through production wells of the subsalt reservoir.

The technical result is also achieved by the fact that in order to eliminate contamination of the bottom-hole zone of the formation and to ensure the maximum possible oil production rate of the subsalt well, hydrocarbon production is carried out during operation of the subsalt well with open bottom, and the produced oil is sent to the suprasalt reservoir, which serves as a temporary underground storage of hydrocarbon raw materials.

The proposed method is implemented as follows. At the oil and gas condensate field planned for development, which incorporates subsalt and suprasalt structures, they restore or create a new complex of production suprasalt wells. The mouth of each well is equipped for fountain operation. In old and depleted suprasalt deposits, the existing well stock and existing infrastructure are used to the maximum extent possible, having adapted it for the fountain operation of suprasalt wells.

In each individual field, consisting of subsalt and suprasalt structures, depending on their size, a special subsalt well is drilled located in the dome of the suprasalt structure. In the roof of subsalt sediments, a technical column is lowered (for example,

- 2,025,574 eight-inch). The descent of the column is carried out according to current technology on an unweighted clay solution until the opening of subsalt deposits.

Before the inflow is called from subsalt sediments in a column filled with a heavier clay solution, a section with perforation openings is distinguished, which is located opposite the productive horizon of the over-salt deposit.

The inflow call is performed with the wellhead closed so that the hydrocarbon feed enters through the perforation holes in the column into the drained overlying productive horizon of the supra-salt reservoir with a pressure equal to the reservoir pressure of the supra-salt horizon, i.e. 4-5 times less than the reservoir pressure of the subsalt horizon. At the same time, oil production rates from the subsalt well can be regulated by the production rates of gushing production pre-salt wells, and the back pressure on the productive subsalt horizon will be offset by the volume of the pre-salt formation into which the pre-salt oil will flow. The optimal operating conditions of the subsalt reservoir during the entire period of oil production will be ensured by the maximum reduction in back pressure on the working reservoir during the development of subsalt reservoirs through the wells of the suprasalt complex. This will prevent the destruction of the bottom-hole zone of the reservoir and ensure free maximum production rates of wells during oil production through suprasalt wells.

In order to maintain the working reservoir pressure above the saturation pressure and increase the coefficient of hydrocarbon extraction into the suprasalt reservoir, associated petroleum gas is pumped into the productive horizons of the suprasalt complex through the perforated section of the technical column acting as an injection well. With a decrease in reservoir pressure, nitrogen is pumped in, a minimum level of depression is achieved in the subsalt reservoir and complete recovery of the geological reserves of the hydrocarbon feed from the subsalt reservoir is achieved.

To exclude contamination of the bottom-hole zone of the formation and to ensure the maximum possible oil production rate of the subsalt well, hydrocarbon production is carried out during operation of the subsalt well with open bottom, and the produced oil is sent to a temporary underground storage of hydrocarbon raw materials, i.e. in the pre-salt deposit. Thus, the challenge of the influx of oil and gas condensate from subsalt deposits when applying the proposed method differs significantly from the existing methods of well development, has a number of significant advantages and solves the problem of creating optimal conditions for opening productive subsalt deposits and further gushing of the subsalt well under conditions similar to conditions open gushing.

The inflow of hydrocarbons is called by open bottom immediately after the opening of the productive horizon with the ideal state of the bottom-hole zone and with a smooth depression on the formation. As a result, the destruction of the bottom-hole zone of the formation is eliminated even with a maximum decrease in back pressure on the working productive formation, which allows preventing formation destruction during the development of the field during oil and gas condensate production. The magnitude of the depression on the productive horizon and its growth dynamics are limited by the processes of penetration (through perforations in the technical column) and saturation of potentially productive layers of the supersalt complex from the subsalt horizon with hydrocarbons. The increase in depression on the main productive horizon proceeds smoothly as the overlying strata are saturated, including, at the final stage, suprasalt structural traps, and this process is regulated by the number and production rates of suprasalt complex wells.

The stage of completion of the filling with subsalt oil or gas condensate of the subsalt reservoir will be indicated by stabilization of the reservoir pressure in this reservoir to a value higher than its initial reservoir or saturation pressure. The decrease in depression on the productive subsalt reservoir is regulated by the operator for oil production by increasing the volume of oil produced by connecting to the fountain production the required additional number of pre-salt production wells or by changing the values of their production rates. Salt oil production through supersalt production wells is carried out under normal flowing conditions with pressures on the productive bottom-hole zone of subsalt deposits not higher than the initial formation pressure of suprasalt deposits. In general, the proposed method for the production of subsalt oil by supersalt complex wells will create the specified conditions for the efficient organization of subsalt oil production, since its production will be carried out under the conditions of the possibility of regulating the level of depression in subsalt reservoirs during production by adjusting the rate of oil extraction with suprasalt wells at optimal reservoir pressure on the subsalt reservoir.

The method will provide the opportunity to develop high-yield oil and gas condensate wells of deep subsalt deposits with useful utilization of associated petroleum gas obtained during separation to provide a period of forced fountain production of hydrocarbons from suprasalt deposits and to increase the oil recovery coefficient in these fields. The proposed method also provides, instead of drilling new special subsalt wells, the use of previously drilled (abandoned or mothballed) subsalt wells.

- 3 025574

The proposed method of oil production, which consists in creating an artificial channel for the flow of oil from underlying productive formations with abnormally high reservoir pressures and significant oil reserves to the upper productive horizons, can be used not only for the production of subsalt oil by supersalt complex wells. In all other cases, when oil and gas complexes and subcomplexes are located in a single open stratigraphic section at various depths, the possibility of creating artificial channels for their vertical relationship can be considered proven. The presence of natural communicating channels in each productive complex along the strike of the layers in combination with artificially created vertical conditions for the interconnection of these productive layers (through an uncemented technical column with perforated holes) is the main condition for the simultaneous production of hydrocarbon raw materials from all underlying productive complexes with abnormally high reservoir pressures wells of the upper productive complexes with small reservoir pressures that As a result, it is more technologically advanced and safer and allows you to fully use the existing infrastructure with less capital investment. Thanks to the proposed method, there is an additional opportunity for the subsalt HC to enter adjacent suprasalt deposits due to possible overflows along the strike of productive suprasalt reservoirs. In this case, from a single artificially created channel for oil from sub-salt to overlying suprasalt deposits, several suprasalt deposits will be restored at once. Thus, one of the main technical results of the present invention is achieved, namely, the amount of construction of super-deep subsalt wells in each field is reduced due to the use of suprasalt wells as production ones. It is possible to use one high-yield subsalt well, which provides simultaneous inflow of subsalt oil to several supersalt oil fields at once with full flow rates of subsalt reservoirs and without backpressure on the productive reservoirs. This achieves another technical result, namely, a decrease in the cost of produced oil due to the difference in the cost and quantity of the required ultra-deep subsalt wells (4500-6000 m deep) and suprasalt (600-1200 m deep), as well as through the use of previously drilled subsalt and pre-salt wells and oil production infrastructure in the region of operations.

Claims (2)

CLAIM 1. The way to develop oil and gas condensate subsalt and supersalt deposits, based on the possibility of using hydrocarbon spills from productive subsalt sediments to supersalt deposits using technical tools for drilling wells, characterized in that each local subsalt structure with a supersalt reservoir located above it is drilled technological subsalt well in the dome of the suprasalt reservoir, while providing the possibility of adjustable vertical flow of coal evodorods from subsalt deposits in the supersalt reservoir due to the installation of a technical column in the well, the perforated area of which is located opposite the productive horizon of the above-salt deposit, and the influx of hydrocarbon raw materials from subsalt deposits is carried out at the closed mouth of the well through the perforated section of the column directly into the suprasalt deposit and after its saturation Hydrocarbon feedstock is recovered in a flowing manner through suprasalt production wells, then to maintain the working formation pressure higher than saturation pressure and increase of hydrocarbon recovery rate through the perforated section of the technical column that functions as an injection well into the supersalt pool in the production horizons of the supersalt complex injected associated petroleum gas, and as the formation pressure decreases, nitrogen is pumped to the minimum level of depression in the subsalt reservoir and ensure the complete extraction of geological reserves of hydrocarbon raw materials subsalt deposits through production wells adsolevoy deposits. 2. The way to develop oil and gas condensate subsalt and supersalt deposits according to claim 1, characterized in that in order to eliminate contamination of the bottomhole formation zone and ensure obtaining the maximum possible oil flow rate in the subsalt well, hydrocarbon raw materials are produced during the operation of the subsalt well by the open bottom, and the extracted oil is directed in the suprasalt reservoir, performing the functions of a temporary underground storage of hydrocarbons.