Disclosure of Invention
Aiming at the defects or shortcomings of the existing fault lateral sealing method, the invention provides a shallow fault lateral sealing evaluation method, which can comprehensively consider the smearing of mudstones to research points in an upper fault tray and a lower fault tray, simultaneously consider the difference of smearing of points at different depths in the mudstones to the research points, and quantitatively characterize the fault lateral sealing.
In order to achieve the purpose, the invention adopts the technical scheme that:
a lateral sealing evaluation method for a shallow fault comprises the following steps:
firstly, collecting lithology data, oil-gas reservoir depth data D and fault distance data T of an upper wall and a lower wall of a fault in a research area;
taking a point with the depth of D in the fault as a research point, taking a depth section [ D, D + T ] as a research range, counting the total number n of mudstones in the disc on the fault, recording the ith mudstone as Hih, wherein i belongs to [1, n ], and counting the thickness delta Hih of each mudstone;
taking points with different depths in the mudstone Hih as independent calculation points, each calculation point has a different distance r from the research point; recording the distance from the research point to the top of the mudstone Hih as rih, and then the value range of r is [ rih, rih + delta Hih ];
ASGR is smeared to the mudstone of the research point by using all the calculation points of single mudstone Hih in the upper disc of the computed tomography of formula (1)HihThe expression of formula (1) is:
the depth segment [ D, D + T ] is divided by the formula (2)]All mudstones on the upper disc of the fault are overlaid on mudstone smearing of the research point, so that smearing ASGR of the mudstone on the upper disc of the fault on the research point can be obtainedh:
Thirdly, taking a point with the depth of D in the fault as a research point, taking a depth section [ D-T, D ] as a research range, counting the total number m of mudstones in the lower wall of the fault, recording the jth mudstone as Hjf, wherein j belongs to [1, m ], and counting the thickness delta Hjf of each mudstone;
taking points of different depths in the mudstone Hjf as independent calculation points, each calculation point has a different distance z from the study point; recording the distance from the research point to the bottom of the mudstone Hjf as rjf, wherein the value range of z is [ rjf, rjf + delta Hjf ];
ASGR is smeared to the mudstone of the research point by using all the calculation points of the single mudstone Hjf in the lower wall of the computed tomography of the formula (3)HjfThe expression of formula (3) is:
the depth segment [ D-T, D ] is divided by the formula (4)]All mudstones in the fault footwall are overlaid on mudstone smearing of the research point, and smearing ASGR of the mudstone of the fault footwall on the research point can be obtainedf:
And (IV) obtaining a fault lateral sealing evaluation result ASGR of the research point by using a formula (5), wherein the expression of the formula (5) is as follows:
fifthly, recording the minimum value of the ASGR result corresponding to the depth D in the fault as a threshold Q; calculating the corresponding ASGR value by taking other points in the fault, which are not the depth D, as research points; the fault lateral sealing performance of the non-depth D research point can be evaluated according to the relation between the Q value and the ASGR value of the non-depth D research point: if the ASGR value of the non-depth D research point is larger than or equal to Q, the research point has fault lateral sealing performance; otherwise, the study point is considered to have no fault lateral seal.
Preferably, in the step (one), the lithological data of the upper wall and the lower wall of the fault is obtained from rock core and rock debris data. All reservoir depth data D are the peak depths of each reservoir.
Preferably, in the calculation processes of the steps (three) to (five), if a single mudstone is away from the research point by the distance z being 0, the mudstone is considered to have the function of laterally sealing oil and gas, and the ASGR value of the research point does not participate in the formulation of the Q value.
Compared with the prior art, the invention has the advantages and positive effects that:
according to the shallow fault lateral sealing evaluation method provided by the invention, the smearing of each mudstone on the research points by each mudstone in the upper fault wall and the lower fault wall can be fully considered, and the smearing difference of points at different depths in each mudstone on the research points is considered, so that the fault lateral sealing can be comprehensively evaluated.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, an embodiment of the present invention provides a shallow fault lateral seal evaluation method, including the following steps:
firstly, collecting lithology data, oil-gas reservoir depth data D and fault distance data T of an upper wall and a lower wall of a fault in a research area;
taking a point with the depth of D in the fault as a research point, taking a depth section [ D, D + T ] as a research range, counting the total number n of mudstones in the disc on the fault, recording the ith mudstone as Hih, wherein i belongs to [1, n ], and counting the thickness delta Hih of each mudstone;
taking points with different depths in the mudstone Hih as independent calculation points, each calculation point has a different distance r from the research point; recording the distance from the research point to the top of the mudstone Hih as rih, and then the value range of r is [ rih, rih + delta Hih ];
ASGR is smeared to the mudstone of the research point by using all the calculation points of single mudstone Hih in the upper disc of the computed tomography of formula (1)HihThe expression of formula (1) is:
the depth segment [ D, D + T ] is divided by the formula (2)]All mudstones on the upper disc of the fault are overlaid on mudstone smearing of the research point, so that smearing ASGR of the mudstone on the upper disc of the fault on the research point can be obtainedh:
Thirdly, taking a point with the depth of D in the fault as a research point, taking a depth section [ D-T, D ] as a research range, counting the total number m of mudstones in the lower wall of the fault, recording the jth mudstone as Hjf, wherein j belongs to [1, m ], and counting the thickness delta Hjf of each mudstone;
taking points of different depths in the mudstone Hjf as independent calculation points, each calculation point has a different distance z from the study point; recording the distance from the research point to the bottom of the mudstone Hjf as rjf, wherein the value range of z is [ rjf, rjf + delta Hjf ];
ASGR is smeared to the mudstone of the research point by using all the calculation points of the single mudstone Hjf in the lower wall of the computed tomography of the formula (3)HjfThe expression of formula (3) is:
the depth segment [ D-T, D ] is divided by the formula (4)]All mudstones in the fault footwall are overlaid on mudstone smearing of the research point, and smearing ASGR of the mudstone of the fault footwall on the research point can be obtainedf:
And (IV) obtaining a fault lateral sealing evaluation result ASGR of the research point by using a formula (5), wherein the expression of the formula (5) is as follows:
fifthly, recording the minimum value of the ASGR result corresponding to the depth D in the fault as a threshold Q; calculating the corresponding ASGR value by taking other points in the fault, which are not the depth D, as research points; the fault lateral sealing performance of the non-depth D research point can be evaluated according to the relation between the Q value and the ASGR value of the non-depth D research point: if the ASGR value of the non-depth D research point is larger than or equal to Q, the research point has fault lateral sealing performance; otherwise, the study point is considered to have no fault lateral seal.
In the method for evaluating lateral sealing performance of a shallow fault, it should be noted that, in the step (i), when the lithological data of the upper wall and the lower wall of the fault is acquired, the lithological data is preferably acquired from rock core and rock debris data. When the depth data D of all hydrocarbon reservoirs are obtained, the vertex depth of each hydrocarbon reservoir is selected as D as an optimal selection for calculation. In the calculation processes of the third step (b) and the fifth step (b), if the distance between a single mudstone and a research point is the condition that z is equal to 0, the mudstone is considered to have the function of laterally sealing oil and gas, and the ASGR value of the research point does not participate in the formulation of the Q value.
In order to describe the lateral sealing performance evaluation method of the shallow fault provided by the embodiment of the invention in more detail, the following description is given with reference to specific embodiments.
Example 1
Taking a northeast reclamation area as a research area, taking a fault F5 as a research object, and respectively locating a reclamation east X1 well and a reclamation east X2 well on an upper disc and a lower disc of a fault F5 (figure 5), wherein the reclamation east X1 well is an oil well and the reclamation east X2 well is a non-oil well; the two wells have distinct exploration results, which show that the lateral sealing of the fault is a key factor for controlling the oil and gas distribution of the region. Mudstone smearing is a key factor for forming lateral sealing of a local fault, and the mudstone smearing principle of the mudstone on the fault shows that (figure 2) the mudstone is divided into mudstone on the upper wall of the fault and mudstone on the lower wall of the fault in the fault moving process, the mudstone on the upper wall of the fault is smeared on the fault by the wedge-shaped part below a research point in the fault, the mudstone on the lower wall of the fault is smeared by the wedge-shaped part above the research point in the fault, and the smearing thickness of the mudstone far away from the mudstone is smaller.
The mudstone has a certain thickness, the distances between each point in the mudstone and a research point are different (figure 2), the minimum distance between the mudstone and the research point on the fault is rih, and the maximum distance between the mudstone and the research point is rih + delta Hih; the distance from the mudstone under the fault to the research point is rjf at minimum and rjf + delta Hjf at maximum. Since the inner points far from the research point have a lower smearing effect on mudstone at the research point than the inner points near the research point, it is necessary to evaluate the lateral fault blocking performance by using the points inside the mudstone as independent calculation points.
To clarify the smearing effect of the mudstone at the research site, the smearing process of the mudstone at the research site by a plurality of mudstones needs to be clarified. Specifically, mudstone smearing for a specific study point is the sum of the smearing effects of n mudstones on the fault and m mudstones on the fault on the study point (fig. 3).
A shallow fault lateral sealing evaluation method for a reclamation northeast region comprises the following steps:
first, collecting the core and debris data of the X1 well and the X2 well in the Tandow as the lithology data of the upper disc and the lower disc of the fault (figure 5 and figure 6), and the position relation between the two wells and the fault F5 is shown in figure 4. The collection pitch T was 20 m. Since the reclaimed X1 well is a producer (fig. 4), the depth at which the hydrocarbon top of the well is located is taken as the depth data D, which are 1171, 1231, 1261, 1333, 1355, 1462, 1466.5, 1565.5m, respectively. Because the reservoir research point already has the oil and gas reservoir, the fault has lateral sealing performance, and the method can provide basis for evaluating the lateral sealing performance of the fault of the subsequent non-reservoir depth research point.
(II) taking a point with the depth of D in the fault as a research point, taking D to D +20m as a research range, taking a hydrocarbon reservoir with the depth of 1231m as an example (figure 6), and taking a 1231-1251m research range, the upper wall of the fault is provided with two mudstones (n is 2) which are respectively named as H1H and H2H, the distances rih between the tops of the mudstones and the research point are respectively 4 and 15m, and the thicknesses delta Hih of the mudstones are both 5m, so that the range of r is [4,9 ] for the mudstone H1H](ii) a For mudstone H2H, r ranges from [15, 20%]. Calculation of ASGR using equation (1)H1hAnd ASGRH2hRespectively 0.81 and 0.29 (the calculation principle refers to figure 3, and the parameters of mudstone position, distance and the like are shown in figure 5). The break can be known by the formula (2)Layer-to-layer plate coating value ASGRhThe value was 0.81+ 0.29-1.10. Similarly, ASGR corresponding to other reservoir depths can be obtainedhValues (table 1).
Table 1 computation table for mudstone smearing of wall on fault to depth D research point
(III) taking a point with the depth of D in the fault as a research point, taking the depth D to D-20m as a research range, taking an oil-gas layer with the depth of 1231m as an example (figure 5), in the research range of 1211-plus 1231m, the lower part of the fault has five mudstones (m is 5) which are respectively named as H1f, H2f, H3f, H4f and H5f, the depths of the bottoms of the five mudstones are 1213, 1216.5, 1218.5, 1223.5 and 1231m, the thicknesses of the five mudstones are delta Hjf and are respectively 2, 0.5, 1.5, 1 and 1.5m, and the distances z between the five mudstones and the research point are respectively [18,20 m]、[14.5,15]、[12.5,14]、[7.5,8.5]And [0,1.5]The application values ASGR of H1f, H2f, H3f and H4f to the study point can be found by the formula (3)HjfThe values are 0.11, 0.03, 0.11 and 0.13 respectively, and the smearing effect ASGR of H1f, H2f, H3f and H4f on the research point in the fault section can be known by the formula (4)fThe value was 0.38. Wherein the distance between the mudstone H5f and the research point is [0,1.5 ]]In the case of 0, it is assumed that this layer of mudstone can necessarily seal the oil and gas in the lateral direction. Similarly, ASGR corresponding to other reservoir depth study points can be obtainedfValues (table 2).
The results of the upper plates of the faults of the reservoir research points 1420m and 1565.5m (table 1) show that the upper plates of the faults have no mudstone in the calculation range, and no mudstone is smeared on the research points, and under the condition that the lower plates of the faults have the mudstone smearing (table 2), the faults can still gather the oil gas (namely, the faults have the lateral sealing performance), so that the geological factor that the lower plates of the faults are smeared on the mudstone of the research points is necessarily introduced.
Table 2 calculation table for mudstone smearing of depth D research point by fault footwall
(IV) ASGR is expressed by the formula (5)hAnd ASGRfThe additions gave the ASGR values for mudstone smearing at the study site (table 3).
TABLE 3 mudstone smear Effect ASGR values for depth D study points
(v) if z is 0 in the 1231 and 1565.5m reservoirs (table 2), and if the threshold Q value is analyzed, the minimum Q value for ASGR for the 1462m reservoir is 0.72, which means that the minimum mudstone smear value for the reservoir is 0.72. Further, comparing the ASGR of the non-depth D research point in the fault with the threshold value of 0.72, the fault blocking performance of the research point can be known. The judgment standard is as follows: if the ASGR value of the non-depth D research point is greater than or equal to 0.72, the research point has fault lateral sealing; otherwise, the study point is considered to have no fault lateral seal.
Taking 1306.5m research sites as an example (fig. 6), only one mudstone on the upper wall of the fault smears the research sites (n ═ 1), and five mudstones on the lower wall of the fault smear the research sites (m ═ 5). The mudstone smearing of the research site by the upper fault wall and the lower fault wall is calculated by using the formula (1) to the formula (4), and the results are shown in the table 4.
TABLE 4 Upper fault wall, lower fault wall, mudstone smearing calculation table for depth 1306.5m research point
Smearing value ASGR of fault upper plate to research point by using formula (5)hAnd the smear value ASGR of the fault lower disc to the research pointfThe result of this addition is 2.59+2.77 to 5.36, which is greater than the threshold Q (0.72), and therefore this point has fault lateral seal.