Detailed correlation medium and small breakpoint identification method for delta front deposit

[0020] In order to make the above-mentioned and other objects, features and advantages of the present invention more obvious and understandable, preferred embodiments are listed below in conjunction with the accompanying drawings, which are described in detail as follows.

[0021] The method for identifying small and medium-sized breakpoints in the delta front sedimentary layer comparison in the present invention establishes the delta front isochronous body through the observation description of the delta front field outcrops, the actual data statistics of the oil field and the theoretical analysis of the sedimentary differentiation principle (I.e. a small layer or single sand body) lithological evolution model along the provenance direction: "sand-lime-mud ternary model", that is, a small layer or single sand body will sequentially appear sandstone and lime sandstone along the provenance direction , Gradually evolved into lime mudstone until pure mudstone. As an interbedded deposit, its lithological change is similar to that of a reservoir, with a law of evolution from physical interbeds (sand) to lime interbeds (ash) and then to argillaceous interbeds (mud) ( figure 2 , image 3 ). This model is applied to the comparison of small layers, so that the comparison work is based on the original basis of marker layers, cycle analysis, etc., and the constraint condition of "isochronic lithology change clues" is added. The point-to-ground comparison method has undergone an innovative change—that is, we invented a new method for comparing small breakpoints—"the same mutation opens the break point, and the different element changes are deposited first", which can accurately identify small breaks of 2-5m. point( Figure 4 ).

[0022] Such as figure 1 As shown, figure 1 It is a flowchart of a specific implementation example of the method for identifying small and medium breakpoints in the delta front sedimentary layer comparison according to the present invention.

[0023] In step 101, first determine the provenance direction, and select the direction along the provenance source as the contrast direction, and carry out the comparison of each well according to this direction ( figure 2 ). The selected direction along the provenance is the contrast direction, and the comparison of the wells in this direction is the basis of this method. Compared with the traditional establishment of a “contrast skeleton network”, the “key There has been a big change in the way to complete the comparison. The flow proceeds to step 102.

[0024] In step 102, the wells with relatively close provenance are regarded as "standard wells" (because the formations of the near provenance wells are relatively well developed), and various logging curves are comprehensively used to judge whether the study well has stratum missing through comparison. The wells near the provenance have relatively complete stratum, which can be used as a standard for comparison, gradually moving away from the provenance and comparing the wells. The required logging curves mainly include spontaneous potential and induction curves, supplemented by natural gamma, acoustic jet lag, and resistivity curves. According to the morphological comparison of logging curves, if it is found that a certain section of the curve of the research well is missing compared with the standard well, it is determined as a stratum missing ( Figure 4 ). When the formation is missing in the well, the process goes to step 103. If there is no stratum missing, the research process of this research well is over (that is, there is no fault or sedimentary change, it is a well with stable sedimentation and can be used as a standard well for the next step), and the analysis of the next well is started.

[0025] In step 103, analyze whether the missing part of the research well and the part corresponding to the standard well (they are the same time unit) belong to the same "element" of the "sand-lime-mud ternary model", that is, the same "element", Gray "yuan" or mud "yuan" is still different from "yuan". That is, according to the established "sand-lime-mud ternary model", the sedimentary analysis is carried out to study whether the lithological environment of the missing part and the part of the standard well (they are isochronous deposits) have the same lithological characteristics. When it is the same "yuan", the process proceeds to step 104; when it is a different "yuan", the process proceeds to step 105.

[0026] In step 104, it is the same "yuan", that is, the missing part of the research well has the same lithology as the corresponding part of the standard well. It means that the same "yuan" deposits are relatively stable, and the missing micro-geological information can be confirmed to be caused by the fault. If the gap is less than 5m, small faults with a drop of 5m or less can be identified. This cannot be confirmed before the invention of this method ( Figure 4 ).

[0027] In step 105, it is a different "element", which is generally a stratum loss caused by sedimentary changes.

[0028] figure 2 This is an illustrative diagram of a mine field of the "sand-ash-mud ternary model" in a specific implementation example of the present invention. It can be seen in the figure that the actual data of the mine field shows: along the material source direction, small layers and interlayers are all It is characterized by the lithological evolution of "sand-lime-mud".

[0029] image 3 It is a schematic diagram of the theory of the "sand-lime-mud ternary model", which is figure 2 On the basis of the research, this law was further verified through field observation and theoretical analysis of sedimentary differentiation principle, and this law was abstracted and systematically graphed.

[0030] Figure 4 This is a comparison and identification map of 2m small breakpoints in a specific implementation example of the present invention. In the figure, the "ternary model" is applied to the small layer comparison, and the "same mutation breaking point, different element changes are deposited first" Compared with the new method, the small breakpoints of 2m are effectively identified, which is the breakpoint with the smallest gap currently recognized.

[0031] Figure 5 to Figure 7 They are all dynamic verification maps of the identified 2m small breakpoints. Based on the 2m small breakpoints identified by geology, the earthquake explained the new small faults, studied the remaining oil-rich areas, deployed and completed the drilling of new wells and achieved good results, which proved this The accuracy of small breakpoints, the importance of identifying such small breakpoints, and the advanced nature of the present invention.