CN112267878B - Tight gas reservoir multilayer development gas well layering yield contribution evaluation method - Google Patents
Tight gas reservoir multilayer development gas well layering yield contribution evaluation method Download PDFInfo
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Abstract
The invention discloses a method for evaluating layered production contribution of a tight gas reservoir multilayer development gas well, which comprises the following steps: step 1) predicting the final accumulated yield of a gas well to be tested; step 2), predicting the bottom hole flow pressure of the gas well to be detected, and comparing the bottom hole flow pressure with the original stratum pressure to obtain a pressure drop; step 3) establishing pressure drop and drainage radius relation graphs of different reservoir types of the block to which the gas well to be tested belongs; step 4) determining the reservoir types of all the small layers of the gas well to be tested, determining the drainage radius of all the small layers of the gas well to be tested according to the pressure drop of the step 2) and the pressure drop and drainage radius relation chart of the different reservoir types of the step 3), and determining the drainage area of all the small layers of the gas well to be tested according to the drainage radius; step 5) determining the yield contribution index of each small layer of the gas well to be tested according to the drainage area of each small layer of the gas well to be tested in step 4); and 6) determining the layering daily yield and the layering final accumulated yield of each small layer of the gas well to be tested, and evaluating layering yield contribution of the gas well to be tested.
Description
Technical Field
The invention belongs to the technical field of natural gas exploitation, and particularly relates to a method for evaluating layered yield contribution of a tight gas reservoir multi-layer development gas well.
Background
The compact gas reservoir enters the middle and later stages of stable production, and the residual reserve is an important means for prolonging the stable production period of the gas field. For multi-layer formation wells, finding the reserve for each formation is the basis for evaluating the remaining reserves.
CN110685651a discloses a method for calculating the contribution of the layered production based on the annual production profile test data and logging interpretation parameters, and establishing the comprehensive relationship between the annual layered production contribution rate of the gas layer component and the logging interpretation parameters.
CN109594981a discloses a method for measuring the underground layered oil gas yield, which obtains the underground layered oil gas yield by measuring the underground layered temperature, the underground geothermal gradient curve and the underground pressure inversion calculation, realizes fixed-point measurement, and has high detection efficiency. However, the tight sandstone gas reservoir is compact and heterogeneous, the temperature and the pressure of the original stratum are different, more than 90% of wells have water production phenomenon, the water production has great influence on the pressure, and the method has certain requirements on the existing production pipe column, so that the method has low universality in certain gas fields and tight sandstone gas reservoirs.
The existing yield layering contribution splitting has no basis, layering is only performed by experience, personal difference is large, various layering tests such as on-site production profile test are large in workload, long in period and high in cost, and an effective and accurate method for evaluating the layering yield of the tight sandstone gas reservoir is not available at present.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a method for evaluating the layering yield contribution of a multi-layer gas well developed by a tight gas reservoir, which overcomes the defects of 1: for tight sandstone gas reservoirs with poor benefits and low cost development strategy, multiple wells participate in the test, and the test is continuously performed for many years, the method is not feasible from the aspects of workload, test cost and time cost; 2: the tight sandstone gas reservoir has compact and heterogeneous structure, the original stratum temperature and pressure are different, more than 90% of wells have water production phenomenon, the produced water has great influence on the pressure, the method has certain requirements on the existing production pipe column, and the existing method has low universality in certain gas fields and tight sandstone gas reservoirs; 3: the existing yield layering contribution splitting has no basis, layering is only performed by experience, personal difference is large, various layering tests such as on-site production profile test are large in workload, long in period and high in cost, and the method for evaluating the layering yield of the tight sandstone gas reservoir is not effective and accurate at present.
In order to solve the technical problems, the technical scheme of the invention is as follows: a method for evaluating the layered production contribution of a tight gas reservoir multi-layer development gas well comprises the following steps:
step 1) predicting the final accumulated yield of a gas well to be tested;
step 2), predicting the bottom hole flow pressure of the gas well to be detected, and comparing the bottom hole flow pressure with the original stratum pressure to obtain a pressure drop;
step 3) establishing pressure drop and drainage radius relation graphs of different reservoir types of the block to which the gas well to be tested belongs;
step 4) determining the reservoir types of all the small layers of the gas well to be tested, determining the drainage radius of all the small layers of the gas well to be tested according to the pressure drop of the step 2) and the pressure drop and drainage radius relation chart of the different reservoir types of the step 3), and determining the drainage area of all the small layers of the gas well to be tested according to the drainage radius;
step 5) determining the yield contribution index of each small layer of the gas well to be tested according to the drainage area of each small layer of the gas well to be tested in step 4);
and 6) determining the layering daily yield and the layering final accumulated yield of each small layer of the gas well to be tested according to the final accumulated yield of the gas well to be tested in the step 1) and the yield contribution index of each small layer of the gas well to be tested in the step 5), and evaluating layering yield contribution of the gas well to be tested.
Preferably, in the predicting the final accumulated yield of the gas well to be measured in the step 1), a yield failure progressive method is adopted to predict the final accumulated yield of the gas well to be measured, the actual yield and the accumulated yield of the gas well to be measured are firstly drawn into a graph, then the relationship between the gas well yield at any moment or the final accumulated yield of the gas well and the initial yield of the gas well is obtained by fitting, then the abandoned yield is given, the time corresponding to the abandoned yield is obtained, and the final accumulated yield corresponding to the time corresponding to the abandoned yield is the final accumulated yield of the gas well to be measured.
Preferably, the gas well production is related to the initial gas well production by:
q g ＝q 0 (1+0.5D 0 t) -2
the relation between the final accumulated production of the gas well and the initial production of the gas well is as follows:
wherein:
q g -gas well production, masterpiece/day;
q 0 -initial production of gas wells, masterpieces/day;
D 0 -gas well initial rate of decline,%;
Q g -final cumulative production of gas wells, in general;
t-time, s.
Preferably, the bottom hole flow pressure calculation formula of the gas well to be measured in the step 2) is as follows:
wherein:
f-vertical deep shaft, m;
γ g -gas specific gravity;
P wh -wellhead casing pressure, MPa (a);
P ws -bottom hole flow pressure, MPa (a);
t-temperature, k;
z-bias factor;
f-coefficient of friction;
p-pressure, pa.
Preferably, the step 3) of establishing pressure drop and drainage radius relation patterns of different reservoir types specifically comprises the following steps: and determining different types of reservoirs according to reservoir classification evaluation criteria established by the block to which the gas well to be tested belongs, then respectively selecting different types of reservoir cores based on an indoor starting pressure gradient test to carry out a multipoint pressure measurement failure type exploitation experiment, and drawing pressure drop and drainage radius relation plates of different types of reservoirs according to experimental results.
Preferably, the different types of reservoirs are divided into: I. II, III, IV, wherein the I, II, III reservoir subdivides two grades a, b.
Preferably, in the step 4), when the ith layer drainage radius of the gas well to be tested is smaller than half a well spacing, namely R i ≦L 1 And (2) the ith layer of the gas well to be tested has the following leakage flow area: ai=pi Ri 2
When the ith layer of the gas well to be tested has a discharge radius between half a well spacing and a row spacing, namely L 1 /2≦R i ≦L 2 And (2) the ith layer of the gas well to be tested has the following leakage flow area: ai=l 2 ×2R i
When the ith layer drainage radius of the gas well to be tested is more than or equal to half row spacing, namely L 2 /2≦R i The ith layer of the gas well to be tested has the following leakage flow area: ai=l 1 ×L 2
Wherein:
ai: small layer drainage area km 2 ；
R i : the radius of the leakage flow of the ith layer is 1-n and m;
n: the number of gas wells drilled when meeting the gas layer;
L 1 : well spacing, km;
L 2 : row spacing, km;
preferably, the calculation formula of the yield contribution index in the step 5) is as follows:
wherein:
I i : yield contribution index, 0.ltoreq.Ai.ltoreq.1, 1.ltoreq.i.ltoreq.n;
n: the number of gas wells drilled when meeting the gas layer;
h i : the thickness of the ith layer is 1-n and m;
ai: small layer drainage area km 2 ；
V: volume of leakage flow, m 3 。
Preferably, the formula of the layered daily output in the step 6) is as follows:
q gi ＝I i ×q g
the formula of the layering final cumulative yield is as follows:
Q gi ＝I i ×Q g
wherein:
q gi : the daily output of the ith layer of gas well is 1-n, and is everything/day;
n: the number of gas wells drilled when meeting the gas layer;
I i : yield contribution index, 0.ltoreq.Ai.ltoreq.1, 1.ltoreq.i.ltoreq.n;
q g : gas well production, masterpiece/day;
Q gi : the accumulated contribution amount of the ith layer is 1-n, and is equal to or less than i-n;
Q g : predicting the final accumulated yield and everything.
Compared with the prior art, the invention has the advantages that:
(1) The method is based on a tight sandstone reservoir seepage rule, a pressure gradient is started under different reservoir physical properties and gas-containing conditions to calculate the small-layer drainage radius, the effective reservoir thickness of the small layer is combined, the drainage volume is calculated in a layered mode, the yield contribution index of each small layer is calculated according to the ratio of the drainage volume of each small layer, then the gas yield of each small layer is obtained, layered yield contribution evaluation of a multi-layer development gas well is realized, the yield contribution index of each layer is based, personal experience is not relied, the difference is small, and therefore the evaluation accuracy is high, and the feasibility is strong;
(2) Aiming at the situation that layering heterogeneous difference exists in multi-layer development of a tight gas reservoir, the invention provides an economic, effective, simple and quick method for evaluating layering yield, the drainage volume of each small layer in different stages can be calculated only by establishing the relation between pressure drop and drainage radius of different types of reservoirs through experiments, so that yield contribution situations of different layers in different stages can be obtained;
(3) The method has no requirement on the existing production pipe column, has high universality on common gas fields and tight sandstone gas reservoirs, and is a method for evaluating the layering yield of the tight sandstone gas reservoirs more effectively and accurately.
Drawings
FIG. 1, example 7 Sux well yield failure progressive prediction graph of the present invention;
FIG. 2 is a plot of pressure drop versus drainage radius for different reservoir types according to example 7 of the present invention;
fig. 3, embodiment 7 of the present invention obtains the drainage radius of each small layer of the gas well to be tested through the pressure drop and drainage radius relation graph version of different reservoir types.
Detailed Description
The following describes specific embodiments of the present invention with reference to examples:
it should be noted that the structures, proportions, sizes and the like illustrated in the present specification are used for being understood and read by those skilled in the art in combination with the disclosure of the present invention, and are not intended to limit the applicable limitations of the present invention, and any structural modifications, proportional changes or size adjustments should still fall within the scope of the disclosure of the present invention without affecting the efficacy and achievement of the present invention.
Also, the terms such as "upper," "lower," "left," "right," "middle," and "a" and the like recited in the present specification are merely for descriptive purposes and are not intended to limit the scope of the invention, but are intended to provide relative positional changes or modifications without materially altering the technical context in which the invention may be practiced.
Example 1
The invention discloses a method for evaluating layered production contribution of a tight gas reservoir multilayer development gas well, which comprises the following steps:
step 1) predicting the final accumulated yield of a gas well to be tested;
step 2), predicting the bottom hole flow pressure of the gas well to be detected, and comparing the bottom hole flow pressure with the original stratum pressure to obtain a pressure drop;
step 3) establishing pressure drop and drainage radius relation graphs of different reservoir types of the block to which the gas well to be tested belongs;
step 4) determining the reservoir types of all the small layers of the gas well to be tested, determining the drainage radius of all the small layers of the gas well to be tested according to the pressure drop of the step 2) and the pressure drop and drainage radius relation chart of the different reservoir types of the step 3), and determining the drainage area of all the small layers of the gas well to be tested according to the drainage radius;
step 5) determining the yield contribution index of each small layer of the gas well to be tested according to the drainage area of each small layer of the gas well to be tested in step 4);
and 6) determining the layering daily yield and the layering final accumulated yield of each small layer of the gas well to be tested according to the final accumulated yield of the gas well to be tested in the step 1) and the yield contribution index of each small layer of the gas well to be tested in the step 5), and evaluating layering yield contribution of the gas well to be tested.
Example 2
Preferably, in the predicting the final accumulated yield of the gas well to be measured in the step 1), a yield failure type progressive method is adopted to predict the final accumulated yield of the gas well to be measured, firstly, the actual yield and the accumulated yield (actual accumulated yield) of the gas well to be measured are drawn into a graph, then, a relation formula between the gas well yield at any moment or the final accumulated yield of the gas well and the initial yield of the gas well is obtained by fitting, then, the abandoned yield is given, the time corresponding to the abandoned yield is obtained, and the final accumulated yield corresponding to the time corresponding to the abandoned yield is the final accumulated yield (predicted accumulated yield) of the gas well to be measured.
The final accumulated production prediction of the gas well is divided into two steps, namely, the production q at any time in application 1 is adopted g And the initial production q of gas well 0 And gas well initial decline rate D 0 And a time relationship, predicting yield at any time; adding the predicted any actual corresponding yield to obtain the final accumulated yield of the gas well; the formula 1 can also be integrated to obtain a relation formula of accumulated gas production of the gas well at any time, and the relation formula is shown in the formula 2.
Preferably, the gas well production is related to the initial gas well production by:
q g ＝q 0 (1+0.5D 0 t) -2 (1)
the relation between the final accumulated production of the gas well and the initial production of the gas well is as follows:
wherein:
q g -gas well production, masterpiece/day;
q 0 -initial production of gas wells, masterpieces/day;
D 0 -gas well initial rate of decline,%;
Q g -final cumulative production of gas wells, in general;
t-time, s.
Example 3
Preferably, the bottom hole flow pressure calculation formula of the gas well to be measured in the step 2) is as follows:
wherein:
f-vertical deep shaft, m;
γ g -gas specific gravity;
P wh -wellhead casing pressure, MPa (a);
P ws -bottom hole flow pressure, MPa (a);
t-temperature, k;
z-bias factor;
f-coefficient of friction;
p-pressure, pa.
The gas pressure in the well bore flow state changes along with the well depth and accords with the formula 3.
To this end, P is wh And P ws Dividing into 2 pressure sections, and performing numerical integration and iteration on the right side of 3Calculating, namely obtaining the bottom hole flow pressure, wherein the right side of the specific calculation formula can be written as formula 4, and carrying out iterative calculation.
Example 4
Preferably, the step 3) of establishing pressure drop and drainage radius relation patterns of different reservoir types specifically comprises the following steps: and determining different types of reservoirs according to reservoir classification evaluation criteria established by the block to which the gas well to be tested belongs, then respectively selecting different types of reservoir cores based on an indoor starting pressure gradient test to carry out a multipoint pressure measurement failure type exploitation experiment, and drawing pressure drop and drainage radius relation plates of different types of reservoirs according to experimental results.
Preferably, the different types of reservoirs are divided into: I. II, III, IV, wherein the I, II, III reservoir subdivides two grades a, b.
The classification evaluation criteria of different types of reservoirs of the block to which the gas well to be tested belongs are the prior art.
Example 5
Preferably, in the step 4), when the ith layer drainage radius of the gas well to be tested is smaller than half a well spacing, namely R i ≦L 1 And (2) the ith layer of the gas well to be tested has the following leakage flow area: a is that i ＝πRi 2
When the ith layer of the gas well to be tested has a discharge radius between half a well spacing and a row spacing, namely L 1 /2≦R i ≦L 2 And (2) the ith layer of the gas well to be tested has the following leakage flow area: a is that i ＝L 2 ×2R i
When the ith layer drainage radius of the gas well to be tested is more than or equal to half row spacing, namely L 2 /2≦R i The ith layer of the gas well to be tested has the following leakage flow area: a is that i ＝L 1 ×L 2
Wherein:
A i : small layer drainage area km 2 ；
R i : the radius of the leakage flow of the ith layer is 1-n and m;
n: the number of gas wells drilled when meeting the gas layer;
L 1 : well spacing, km;
L 2 : row spacing, km;
preferably, the calculation formula of the yield contribution index in the step 5) is as follows:
wherein:
I i : yield contribution index, 0.ltoreq.Ai.ltoreq.1, 1.ltoreq.i.ltoreq.n;
n: the number of gas wells drilled when meeting the gas layer;
h i : the thickness of the ith layer is 1-n and m;
A i : small layer drainage area km 2 ；
V: volume of leakage flow, m 3 。
Example 6
Preferably, the formula of the layered daily output in the step 6) is as follows:
q gi ＝I i ×q g
the formula of the layering final cumulative yield is as follows:
Q gi ＝I i ×Q g
wherein:
q gi : the daily output of the ith layer of gas well is 1-n, and is everything/day;
n: the number of gas wells drilled when meeting the gas layer;
I i : yield contribution index, 0.ltoreq.Ai.ltoreq.1, 1.ltoreq.i.ltoreq.n;
q g : gas well production, masterpiece/day;
Q gi : the accumulated contribution amount of the ith layer is 1-n, and is equal to or less than i-n;
Q g : the final cumulative yield is predicted and the total,is a everything.
Example 7
The well spacing of the block of the threx well is 600m, the row spacing is 800m, the original stratum pressure is 32MPa, the reservoir classification evaluation standard is established in the region, the pressure drop and drainage radius relation graph of different types of reservoirs is established through a seepage experiment, and the layering final accumulated gas production of the well is calculated.
Step 1) final cumulative production prediction for gas wells
Plotting actual and cumulative production of threo wells, see fig. 1, under known initial production and initial rate of decline of gas wells, applying equations 1 and 2 to calculate the actual and cumulative production of the fitted threo wells until the predicted curve fully coincides with the actual data points, then giving a 0.1 x 10 4 m 3 The abandoned yields per d were extrapolated over time for the gas well yields and cumulative yields according to equations 1 and 2, with the corresponding cumulative yields for the abandoned yields being the final cumulative yields for the gas well, predicted threo as 6070.4 x 10 for the final cumulative yields for the well 4 m 3 。
Step 2) bottom hole flow pressure conversion
The well casing pressure is 10.4MPa in a certain day, and the daily yield of the well is 1.3356 multiplied by 10 4 m 3 The bottom hole flow pressure of the well is converted to be 14.2MPa by adopting the formula 3.
Step 3) pressure drop and drainage radius relation graph plate establishment of different reservoir types
According to the actual situation of the block, the reservoir is classified into I, II, III, IV types according to the existing reservoir classification standard of the block, and the first three reservoirs with development value are subdivided into two grades a and b (table 1) as shown in table 1.
Table 1 su x block reservoir classification evaluation criteria
Based on an indoor starting pressure gradient test, different types of reservoir cores are selected respectively to carry out a multipoint pressure measurement failure type exploitation experiment, a graph of the relation between pressure drop and drainage radius of different types of reservoirs is drawn according to experimental results, as shown in fig. 2, and a graph of the relation between pressure drop and drainage radius of different types of reservoirs is established.
Step 4) determining the small layer drainage radius and drainage area
Threo-well three small layers are involved in production, wherein layer 1 is interpreted as a gas layer, 8m thick, permeability 1.2mD, gas saturation 72%, layer la rated according to table 1, layer 2 is interpreted as a gas layer, 5.5m thick, permeability 0.2mD, gas saturation 58%, mb rated, layer 3 is interpreted as a gas layer, 3m thick, permeability 0.7mD, gas saturation 64%, and mb rated.
When the bottom hole pressure is 14.2MPa in a certain day, the pressure difference between the bottom hole pressure and the original stratum pressure (the original stratum pressure of the target layer of the block is about 32 MPa) is 17.8MPa. When the well is abandoned, the well bottom hole flow pressure is 1.5MPa (the value can be calculated through the step 2), the existing conventional value can also be used, and the pressure difference between the well bottom hole flow pressure and the original stratum pressure is 30.5MPa.
As can be seen from fig. 3, when the differential pressure is 17.8MPa, the drainage radius of layer 1 is greater than 1000m and greater than half the pitch 400m; the drainage radius of the layer 2 is 50m and is smaller than 300m of half well spacing; and the drainage radius of the layer 3 is 190m and is smaller than half well spacing.
When the pressure difference is 30.5MPa, the drainage radius of the layer 1 is more than 1000m and more than half row spacing 400m; the drainage radius of the layer 2 is 100m and is smaller than 300m of half well spacing; the drainage radius of layer 3 is 400m, which is equal to half row pitch.
When the differential pressure was 17.8MPa, the stratified discharge area was calculated as follows:
the 1 st layer has a discharge radius larger than half a row distance, and the 1 st layer has a discharge area of
A 1 ＝L 1 ×L 2 ＝600m×800m＝0.48km 2
The 2 nd layer leakage flow radius is smaller than half well spacing, the 2 nd layer leakage flow area is
A 2 ＝π×(50m) 2 ＝0.0078km 2
The 3 rd layer of drainage radius is between half well spacing and half row spacing, the 3 rd layer of drainage area is
A 3 ＝π×(190m) 2 ＝0.1134km 2
When the differential pressure was 30.5MPa, the stratified discharge area was calculated as follows:
the 1 st and 3 rd layers have a discharge radius of half row spacing or more, and the 1 st and 3 rd layers have a discharge area of
A 1 ＝A 3 ＝L 1 ×L 2 ＝600m×800m＝0.48km 2
The 2 nd layer leakage flow radius is smaller than half well spacing, the 2 nd layer leakage flow area is
A 2 ＝π×(100m) 2 ＝0.031km 2
Step 5) yield contribution index determination
The effective thickness of the three small layers is 8m, 5.5m and 3m respectively.
When the pressure difference is 17.8MPa, the total volume of the well leakage flow is
V＝8m×0.48km 2 +5.5m×0.0078km 2 +3m×0.1134km 2 ＝4.223m·km 2
Layer 1 yield contribution index of
I 1 ＝8m×0.48km 2 /4.223m·km 2 ＝0.91
Layer 2 yield contribution index of
I 2 ＝5.5m×0.07km 2 /4.223m·km 2 ＝0.01
Layer 3 yield contribution index of
I 3 ＝3m×0.48km 2 /4.223m·km 2 ＝0.08
When the pressure difference is 30.5MPa, the total volume of the well leakage flow is
V＝8m×0.48km 2 +5.5m×0.031km 2 +3m×0.48km 2 ＝5.4505m·km 2
Layer 1 yield split index of
I 1 ＝8m×0.48km 2 /5.4505m·km 2 ＝0.71
Layer 2 yield split index of
I 2 ＝5.5m×0.031km 2 /5.4505m·km 2 ＝0.03
Layer 3 yield split index of
I 3 ＝3m×0.48km 2 /5.4505m·km 2 ＝0.26
Step 6) determination of layered daily yield
When the bottom hole flow pressure of the well is 14.2MPa in a certain day, the yield is 1.3356 multiplied by 10 4 m 3 The split yield of each layer in the day is respectively as follows:
layer 1 yield of
q g1 ＝I 1 ×q g ＝0.91×1.33×10 4 m 3 ＝1.21×10 4 m 3
Layer 2 yield of
q g2 ＝I 2 ×qg＝0.01×1.33×10 4 m 3 ＝0.01×10 4 m 3
Layer 3 yield of
q g3 ＝I 3 ×qg＝0.08×1.33×10 4 m 3 ＝0.11×10 4 m 3
Layering and finally accumulating gas production
When the bottom hole pressure is the bottom hole waste stream pressure (1.5 MPA), the final accumulated gas yield is predicted to be 6070.4 multiplied by 10 4 m 3 The gas well leakage radius is the maximum control radius, and in this case, the gas production corresponding to each small layer is the final accumulated gas production of the small layer prediction.
Layer 1 yield of
Q g1 ＝I 1 ×Qg＝0.71×6070.4×10 4 m 3 ＝4310.0×10 4 m 3
Layer 2 yield of
Q g2 ＝I 2 ×Qg＝0.03×6070.4×10 4 m 3 ＝182.1×10 4 m 3
Layer 3 yield of
Q g3 ＝I 3 ×Qg＝0.26×6070.4×10 4 m 3 ＝1578.3×10 4 m 3
The layering yield contribution evaluation is carried out on the gas well to be tested, three small layers of the well participate in production, and when the bottom hole flow pressure of the well is 14.2MPa in a certain day, the yield is 1.3356 multiplied by 10 4 m 3 Layer 1 yield of 1.21×10 4 m 3 Layer 2 yield of 0.01X10 4 m 3 Layer 3 yield of 0.11×10 4 m 3 The method comprises the steps of carrying out a first treatment on the surface of the When the well is abandoned, the final accumulated gas yield is predicted to be 6070.4 multiplied by 10 when the well bottom abandoned flow pressure is 1.5MPA 4 m 3 Layer 1 yield is 4310.0 ×10 4 m 3 Layer 2 yield 182.1X10 4 m 3 Layer 3 yield is 1578.3 ×10 4 m 3 。
When in actual exploitation production, the predicted layered daily output and the predicted layered final accumulated output are basically the same as the actual layered daily output and the predicted layered final accumulated output, and the accuracy rate is more than 90 percent.
The principle of the invention is as follows:
the method comprises the steps of firstly predicting the final accumulated output and bottom hole flow pressure of a gas well to be detected, comparing the final accumulated output and the bottom hole flow pressure with the original stratum pressure to obtain a pressure drop, then establishing a pressure drop and drainage radius relation graph of different reservoir types in an area of the gas well to be detected, corresponding the gas well to be detected to different reservoir types in the area, obtaining the drainage radius according to the pressure drop on the graph, obtaining the drainage volume according to the drainage radius, and calculating the yield contribution index of each small layer according to the ratio of the drainage volume of each small layer because the drainage volume is in close proportion to the yield, obtaining the gas yield of each small layer, and evaluating the layering yield contribution of the multi-layer development gas well.
The method is based on a tight sandstone reservoir seepage rule, calculates the small-layer drainage radius by starting the pressure gradient under different reservoir physical properties and gas-containing conditions, combines the small-layer effective reservoir thickness, calculates the drainage volume in a layered manner, calculates the yield contribution index of each small layer according to the ratio of the drainage volume of each small layer, and then obtains the gas yield of each small layer to realize layered yield contribution evaluation of a multi-layer development gas well.
Aiming at the situation that layering heterogeneous difference exists in multi-layer development of a tight gas reservoir, the invention provides an economic, effective, simple and quick method for evaluating layering yield, the drainage volume of each small layer at different stages can be calculated only by establishing the relation between pressure drop and drainage radius of different types of reservoirs through experiments, so that yield contribution situations of different layers at different stages can be obtained.
The method has no requirement on the existing production pipe column, has high universality on common gas fields and tight sandstone gas reservoirs, and is a method for evaluating the layering yield of the tight sandstone gas reservoirs more effectively and accurately.
While the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes may be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Many other changes and modifications may be made without departing from the spirit and scope of the invention. It is to be understood that the invention is not to be limited to the specific embodiments, but only by the scope of the appended claims. The components and structures not specifically described in this embodiment are well known in the art and are not described in detail herein.
Claims (2)
1. The method for evaluating the layered production contribution of the tight gas reservoir multi-layer development gas well is characterized by comprising the following steps of:
step 1) predicting the final accumulated yield of a gas well to be tested;
step 2), predicting the bottom hole flow pressure of the gas well to be detected, and comparing the bottom hole flow pressure with the original stratum pressure to obtain a pressure drop;
step 3) establishing pressure drop and drainage radius relation graphs of different reservoir types of the block to which the gas well to be tested belongs;
step 4) determining the reservoir types of all the small layers of the gas well to be tested, determining the drainage radius of all the small layers of the gas well to be tested according to the pressure drop of the step 2) and the pressure drop and drainage radius relation chart of the different reservoir types of the step 3), and determining the drainage area of all the small layers of the gas well to be tested according to the drainage radius;
step 5) determining the yield contribution index of each small layer of the gas well to be tested according to the drainage area of each small layer of the gas well to be tested in step 4);
step 6) determining layering daily yield and layering final accumulated yield of each small layer of the gas well to be tested according to the final accumulated yield of the gas well to be tested in the step 1) and the yield contribution index of each small layer of the gas well to be tested in the step 5), and evaluating layering yield contribution of the gas well to be tested;
the calculation formula of the yield contribution index in the step 5) is as follows:
wherein:
I i : yield contribution index, 0.ltoreq.Ai.ltoreq.1, 1.ltoreq.i.ltoreq.n;
n: the number of gas wells drilled when meeting the gas layer;
h i : the thickness of the ith layer is 1-n and m;
ai: small layer drainage area km 2 ；
V: volume of leakage flow, m 3 ；
Predicting the final accumulated yield of the gas well to be detected in the step 1) is to predict the final accumulated yield of the gas well to be detected by adopting yield failure progressive method, firstly, drawing the actual yield and the accumulated yield of the gas well to be detected into a graph, then fitting to obtain a relation between the gas well yield at any moment or the final accumulated yield of the gas well and the initial yield of the gas well, then giving out waste yield to obtain the time corresponding to the waste yield, wherein the final accumulated yield corresponding to the time corresponding to the waste yield is the final accumulated yield of the gas well to be detected;
the relation between the gas well yield and the initial gas well yield is as follows:
the relation between the final accumulated production of the gas well and the initial production of the gas well is as follows:
wherein:
q g -gas well production, masterpiece/day;
q 0 -initial production of gas wells, masterpieces/day;
D 0 -gas well initial rate of decline,%;
Q g -final cumulative production of gas wells, in general;
t-time, s;
the bottom hole flow pressure calculation formula of the gas well to be measured in the step 2) is as follows:
wherein:
f-vertical deep shaft, m;
γ g -gas specific gravity;
P wh -wellhead casing pressure, MPa (a);
P ws -bottom hole flow pressure, MPa (a);
t-temperature, k;
z-bias factor;
f-coefficient of friction;
p-pressure, pa;
the step 3) of establishing pressure drop and drainage radius relation plates of different reservoir types comprises the following specific steps: determining different types of reservoirs according to reservoir classification evaluation criteria established by a block to which a gas well to be tested belongs, then respectively selecting different types of reservoir cores based on an indoor starting pressure gradient test to carry out a multipoint pressure measurement failure exploitation experiment, and drawing pressure drop and drainage radius relation plates of different types of reservoirs according to experimental results;
the different types of reservoirs are divided into: I. II, III, IV, wherein the I, II, III reservoir subdivisions a, b are of two grades;
in the step 4), when the leakage radius of the ith layer of the gas well to be tested is smaller than half well spacing, namely R i ≦L 1 And (2) the ith layer of the gas well to be tested has the following leakage flow area: ai=pi Ri 2
When the ith layer of the gas well to be tested has a discharge radius between half a well spacing and a row spacing, namely L 1 /2≦R i ≦L 2 And (2) the ith layer of the gas well to be tested has the following leakage flow area: ai=l 2 ×2R i
When the ith layer drainage radius of the gas well to be tested is more than or equal to half row spacing, namely L 2 /2≦R i The ith layer of the gas well to be tested has the following leakage flow area: ai=l 1 ×L 2
Wherein:
ai: small layer drainage area km 2 ；
R i : the radius of the leakage flow of the ith layer is 1-n and m;
n: the number of gas wells drilled when meeting the gas layer;
L 1 : well spacing, km;
L 2 : row pitch, km.
2. The method for evaluating the layered production contribution of a tight gas reservoir multi-layer developed gas well according to claim 1, wherein the formula of the layered daily production in the step 6) is as follows:
q gi =I i ×q g
the formula of the layering final cumulative yield is as follows:
Q gi =I i ×Q g
wherein:
q gi : the daily output of the ith layer of gas well is 1-n, and is everything/day;
n: the number of gas wells drilled when meeting the gas layer;
I i : yield contribution index, 0.ltoreq.Ai.ltoreq.1, 1.ltoreq.i.ltoreq.n;
q g : gas well production, masterpiece/day;
Q gi : the accumulated contribution amount of the ith layer is 1-n, and is equal to or less than i-n;
Q g : predicting the final accumulated yield and everything.
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| RU2285790C1 (en) * | 2005-04-12 | 2006-10-20 | Закрытое акционерное общество "УфаНИПИнефть" | Method to control stacked pool oil deposit development with the use of residual net oil maps |
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