RU2105136C1 - Method of determining location stagnant and low-drainable zones of oil deposits - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: section of oil deposit with production and injection wells is chosen, for each production well of which, accumulated oil take-off, water, well operation time, formation oil saturation, and then deposit well drainage capacity are determined. Deposit drainage capacity is mapped and, on chosen sector of oil deposit, current oil reserve and current oil saturation are determined, after which maps of current oil reserve and current oil saturation are drawn. On each of the drawn maps, low drainable and stagnant zones are preliminarily chosen and chosen zones on all maps are compared. Low drainable and stagnant zones stated those zones which coincide with each other on all maps. EFFECT: facilitated effective exploitation of oil deposit. 3 dwg

Description

 The invention relates to the oil industry, in particular, to the development of oil fields.

 A known method for determining the location of stagnant and weakly drained zones of an oil deposit, including selecting a section of an oil deposit with producing and injection wells, determining for each producing well the accumulated selection of oil, liquid and water, operating time of the well and oil-saturated reservoir power, determining the coefficient of drainage by the wells of the reservoir, constructing reservoir drainability maps [1].

 The disadvantage of this method is that it does not take into account the complexity of the geological structure of the oil reservoir, that is, the presence of interlayers, their variable power over the area of the reservoir, various types of heterogeneities and disturbances. Therefore, the constructed drainage maps do not give a complete picture of the drainability, namely, the recoverable reserves of oil-saturated sections of the reservoir, which subsequently, when redeveloping the reservoir, leads to irrational placement of wells, namely, in places where there are no recoverable oil reserves or generally in non-oil-saturated sections of the reservoir.

 The aim of the invention is to increase the accuracy of determining the location of stagnant and slightly drained zones of oil deposits, and, as a result, accelerate the pace of development, increase oil recovery and reduce the consumption of material and labor costs.

 This goal is achieved in that in a method for determining the location of stagnant and weakly drained zones of an oil deposit, including selecting a section of an oil deposit with producing and injection wells, determining for each producing well the accumulated selection of oil, liquid and water, the operating time of the well and the oil-saturated thickness of the formation, determining the coefficient of drainage by wells of the reservoir, the construction of maps of the drainability of the reservoir, in the selected area of the oil reservoir, the current oil supply and the current oil saturation, maps of the current oil supply and current oil saturation are built, preliminary on each of the maps constructed and weakly drained and stagnant zones are distinguished, the selected zones on all maps are compared and areas in the selected zones that coincide on all maps are taken for weakly drained and stagnant oil deposits.

 The method is as follows.

 1. Choose a site of oil deposits with producing and injection wells.

2. For each production well, the accumulated selection of oil, liquid and water Q _i , the operating time of the well T _i and the oil-saturated reservoir power h _{i are} determined.

3. Determine the coefficient of drainability D _i from the following relationship
D _i = Q _i / (T _i xh _i ),
where D _i - drainage coefficient, m ² / day;
Q _i - cumulative selection of oil or liquid or water, m ³ ;
T _i - well operation time, days;
h _i - oil-saturated thickness of the reservoir, m

The reduced drainage coefficient is determined by the dependence
P _i = D _i / D _max
where P _i is the reduced coefficient of drainability;
D _i - drainage coefficient, m ² / day;
D _max - the maximum value of the coefficient of drainability, m / day

 4. Construct drainage maps for oil, liquid and water from the values of the reduced drainage coefficient — maps of equal values of the reduced drainage coefficients.

To build maps, the given drainage coefficients for wells are divided into levels with any step. The obtained equal levels from well to well are connected by solid contours. Contours with reduced drainage coefficient equal to zero (P _i = 0) characterize the lack of drainability and, therefore, the zone is stagnant. Isolines above zero with a minimum reduced drainage coefficient characterize weakly drained zones.

 5. On the drainage maps for oil, liquid and water, pre-stagnant and slightly drained zones are distinguished, that is, zones limited by contours with equally low reduced drainage coefficients.

 6. Determine the current oil saturation in the selected area of the reservoir.

 7. Build a map based on the values of the current oil saturation. Contour lines with maximum oil saturation characterize weakly drained and stagnant zones.

 8. On the map, stagnant and slightly drained zones are preliminarily identified by the values of the current oil saturation.

9. In the selected section of the reservoir, the current oil reserve and the current oil reserve coefficients are determined as the ratio of the current oil reserve V _iT to the maximum value of the initial oil reserve V _max (usually the distribution of its initial reserves and initial oil saturation is determined during the development of the oil reservoir).

 10. Build a map of the current oil reserve by the values of the coefficients of the current oil reserve. The contours with the maximum values of the coefficients of the current oil reserve characterize stagnant and slightly drained zones.

 11. On the map of the current oil reserve, poorly drained and stagnant zones are preliminarily identified.

 12. Compare the selected zones on all maps and for stagnant and weakly drained zones take sites in the selected zones that match on all maps.

 Maps of the current oil reserve and current oil saturation show the distribution in the selected area of the current oil reserve and current oil saturation.

 Example 1. A site is selected for oil deposits, including 34 producing and 16 injection wells.

 Based on the measurements, a file of initial field information is generated, which is necessary to determine the drainage coefficient, current oil saturation, and current oil reserves. The specified information contains basic data on the flow rate of liquid, oil and water, accumulated oil, liquid and water withdrawal, oil-saturated reservoir power, well operating time, formation permeability and porosity, formation pressure, oil and water viscosity.

 2. Based on field information, using the software package determines the coefficients of drainability, current oil saturation and current oil reserves.

 3. Construct drainage maps for oil, liquid and water from the values of drainage coefficients. In FIG. 1 shows a map of oil drainability. The same map is built for liquid and water. On drainage maps, stagnant and slightly drained zones are distinguished, that is, zones limited by contours with minimal reduced drainage coefficients. In the example, these are zones limited by contours with a reduced drainage coefficient equal to 0.02 (see figure 1).

 4. Build a map of the current oil saturation in the selected area (figure 2). On the map of the current oil saturation, weakly drained and stagnant zones are defined, limited by contours with maximum values of the oil saturation coefficient. In the example, these are zones limited by contours with a coefficient of 0.8-0.9.

 5. Build a map of current oil reserves based on the values of the coefficient of current oil reserves. On the map, zones are identified that are slightly drained and stagnant, that is, zones limited by contours with maximum values of the coefficient of the current oil supply. In the example, these are zones limited by contours with a maximum coefficient of the current oil supply equal to 0.5-0.6 (Fig. 3).

 6. Compare selected areas.

 Comparison of drainage maps with maps of current oil saturation and current oil reserves shows that the areas in the selected zones on these maps do not coincide, namely, some of the sections with minimal values of the drainage coefficient are located in places with low oil saturation and low values of current oil reserves (see. Fig. 1-3). This indicates that in these areas there is no possibility of additional oil production. At the same time, the coincidence of areas in the selected zones on all maps indicates that there is a reserve in these areas to achieve the potential for additional oil production by introducing adjustments to the development system of these areas of the oil reservoir.

 Thus, the proposed method allows to increase the accuracy of determining the location of stagnant and slightly drained zones of oil deposits.

Claims (1)

 A method for determining the location of stagnant and weakly drained zones of an oil deposit, including selecting a section of an oil deposit with producing and injection wells, determining for each producing well the accumulated selection of oil, liquid and water, the operating time of the well and the oil saturated capacity of the formation, determining the coefficient of drainage by the wells of the reservoir, mapping drainability of the reservoir, characterized in that in the selected area of the oil reservoir determine the current oil supply and current oil saturation b, maps of the current oil supply and current oil saturation are constructed, previously weakly drained and stagnant zones are selected on each of the maps constructed, the selected zones on all maps are compared, and the areas in the selected zones that coincide on all maps are taken as weakly drained and stagnant zones of the oil deposit.

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