An Evaluation Method of Fault Sealing

Abstract

The invention relates to a method for evaluating the fault sealing property in the technical field of oil and gas field exploration. The method includes the steps of (1) selecting a breakpoint in needof sealing property evaluation on a fault that is dislocated in a reservoir stratum, determining each sand-mud stratum with relative wall slip through the breakpoint, and determining the thickness [delta]Zi of each sand-mud stratum; (2) sequentially acquiring the shale content Vshi of each sand-mud stratum slipping through the breakpoint; (3) sequentially solving for a weighting coefficient Wi slipping through each sand-mud stratum; (4) calculating a weighted mudstone fault mud ratio WSGR value of the breakpoint; and (5) evaluating the sealing property of the reservoir at the breakpoint location by using the weighted mudstone fault mud ratio WSGR value, when the WSGR value is greater than or equal to 0.6, indicating that the fault sealing property of the breakpoint location is good and the oil and gas can be effectively sealed, determining the reservoir stratum as an oil stratum or an oil-bearing water stratum with a large probability, and determining the reservoir stratum as a waterstratum with a large probability otherwise. The method fully considers the docking relationship between the two walls of the fault, adds the distance coefficient to reflect the contribution degree ofeach relative wall point on the calculation point, and improves the accuracy and precision of the judgment of the fault sealing property.

Description

technical field [0001] The invention relates to a fault sealing evaluation method, in particular to the fault sealing evaluation of fault block traps, and belongs to the technical field of oil and gas field exploration. Background technique [0002] Trap refers to a space with the conditions for oil and gas accumulation. It generally consists of three parts: reservoirs; cap rocks that prevent oil and gas from escaping; barriers that prevent oil and gas from continuing to migrate and cause oil and gas accumulation in all aspects, such as anticlines, faults, lithological pinch-outs, and unconformity barriers. There are mainly three types of traps: structural traps, stratigraphic traps and hydrodynamic traps. When oil and gas accumulate in traps with a unified pressure system and oil-water boundary, it is a oil and gas reservoir. [0003] Because faults dislocate the reservoirs, the oil and gas that originally migrated in the updip direction are blocked, thus forming fault-sh...

AI Technical Summary

Problems solved by technology

However, this method also has shortcomings: on the one hand, it does not consider the docking relationship of the calculation points, which will lead to judgment errors; on the other hand, due to the lack of data of unsealed faults in the statistical model, misjudgment of unsealed faults will occur. There may be large errors in the judgment of fault sealing

[0011] From the perspective of technical application fields, the main reason for these problems and defects is that the fault gouge ratio method uses the percentage of shale or clay within the fault range to express the smearing ability of mudstone, which treats the accumulated mudstone as a layer of mudstone, but Since the distribution of mudstone also affects the strength of mudstone smear, this method is only suitable for formations with relatively uniform mudstone thickness distribution, and the scope of application is relatively limited

Moreover, this formula is actually the mudstone content within the range of the fault throw, and cannot reflect the contribution of mudstone at each point to the sealing of the target position

In addition, this method does not take into account the difference in lithology of the jointed disk at the calculation point. When the fault throw is the same and the mudstone thickness in the fault throw is the same, but the lithology of the jointed disk at the calculation point is different (mudstone or sandstone), although the calculated SGR value the same, but the sealing capacity of faults may be quite different

Images