Method for representing corrosion evolution of fractured lake basin carbonate reservoir stratum by tectonic movement

Abstract

The invention discloses a method for representing corrosion evolution of a fractured lake basin carbonate reservoir by tectonic movement, and belongs to the technical field of oil and gas reservoir geological evaluation. The method comprises the following steps: firstly, establishing a karst vertical distribution mode in an adjacent outcrop area by adopting'four-point calibration '; secondly, based on an outcrop mode, clamping an underground structure-karst interface and a range by utilizing multi-information fusion of well drilling, rock core and well logging; thirdly, quantifying the independent corrosion contribution of different-period tectonic movement of a single well point by adopting a layer-by-layer decreasing method; and finally, constructing a trinity model by taking single well data as a point, a regional trend as a line and an earthquake inversion three-dimensional body as a surface, and dynamically recovering a multi-stage structure-karst evolution process. According to the method, the fine quantitative characterization of the multi-stage superposition type rock reservoir is realized, and the technical advantage of quantitative characterization of the multi-stage corrosion transformation of the carbonate rock is formed.

Description

Technical Field

[0001] This invention relates to the technical field of dissolution and stimulation of carbonate reservoirs in oil and gas basins. Specifically, it is a method for characterizing the dissolution and evolution process of carbonate reservoirs based on the fusion of multiple data sources, including drilling, core, logging, and seismic data. Background Technology

[0002] In oil and gas basins, especially in the rift basins of eastern China, basins formed by multiple tectonic movements are vertically superimposed to form superimposed basins. These superimposed basins, having undergone multiple tectonic movements, not only result in multiple sets of source rocks superimposed on each other, with multiple source rocks simultaneously supplying hydrocarbons to the reservoirs, but also in the cross-distribution of various reservoir types, thus exhibiting an orderly distribution of various types of oil and gas reservoirs within the basin. For the same type of carbonate rock strata, multiple tectonic movements cause weathering and leaching, forming ancient buried hill oil and gas reservoirs with karst zones as reservoirs. For example, the Renqiu buried hill well Ren 4 (producing thousands of tons per day) and Ren 9 (even reaching a high production record of 5,000 tons per day) reveal that reservoirs mainly composed of dissolution fractures and cavities formed by carbonate karst are a crucial reservoir type in rift basins.

[0003] Research methods on carbonate karst (karst) involve multiple aspects (Song Laiming et al., 2005), including petrology, geochemistry, inclusions, drilling and logging, and well logging, i.e., seismic analysis. Wu Kongyou et al. (2010) determined the zonation and planar distribution of karst zones based on drilling and well logging methods. Qian Haitao et al. (2014) proposed a stress-dissolution coupling relationship under geostress. Xu Xiaosong et al. (2006) and Wu Kongyou (2010) classified carbonate karst from the Tarim Basin's northern and central sections and the Bohai Bay Basin's central depression, respectively, establishing different karst models and even using seismic inversion to predict carbonate karst (Yu Yixin, 2006). Therefore, it is evident that a systematic method for quantitatively reconstructing the karst evolution history of superimposed basins in oil and gas-bearing basins has not yet been formed, although the existing karst descriptions are relatively complete.

[0004] As oil and gas exploration gradually shifts towards deeper layers, characterizing carbonate karst reservoirs formed by different tectonic movements has become a crucial research topic. In the Shengli Oilfield exploration area, multiple wells have cored carbonate karst zones, establishing complete drilling, logging, and well logging data. This has revealed the stratigraphic contact relationships corresponding to sedimentary discontinuities formed by multiple tectonic movements, providing comprehensive data for quantitatively characterizing the evolution of carbonate reservoir dissolution caused by multiple tectonic movements. Guided by the development model of karst zones in outcrops, and based on delineating complete carbonate karst zones in the overburden area, a phased "gradually decreasing" method is used to characterize the width of karst zones formed by different tectonic movements. Combined with seismic inversion results, the karst boundaries of different tectonic movements are delineated, enabling the reconstruction of the karst zone evolution process and overcoming the current challenge of vertically segmenting multiple karst zones. Summary of the Invention

[0005] This invention provides a method for characterizing the dissolution and evolution of carbonate reservoirs in rift basins caused by tectonic movements, achieving the objective of the invention through the following means: (1) A four-point calibration method was used to calibrate the outcrop areas adjacent to the study area to determine the response characteristics of carbonate rock dissolution caused by key tectonic movements in the exposed carbonate rocks. (2) Based on the key tectonic movement interface marked in the outcrop area, the top and bottom of the carbonate rock strata and the overlying strata are accurately identified by combining well logging, well logging and seismic analysis; the key tectonic movement interface and its dissolution range are determined by combining well response positioning, core characterization as a supplement and well log response alignment. (3) The key well locations of each carbonate stratum in the study area were selected. Using the method of "overlying strata constraint and layered control", the alteration effect of different tectonic movements on the dissolution of carbonate reservoirs was quantitatively characterized from bottom to top in the manner of "layer-by-layer reduction". (4) The tectonic evolution process of carbonate reservoir karst is constructed by adopting a method based on single well points, guided by outcrop tectonic models, and centered on seismic response characteristics.

[0006] The effects of the invention: The advantages of this invention are: it establishes a correspondence between tectonic movements and their corresponding carbonate karstification, and proposes a calculation method based on the gradual decrease in karst thickness to characterize the thickness distribution of carbonate karstification zones formed by different tectonic movements, providing new research ideas and technical means for the prediction of carbonate karstification in rift basins. Attached Figure Description

[0007] Figure 1 Flowchart of a method for characterizing the dissolution evolution of carbonate reservoirs in rift basins caused by tectonic movements; Figure 2Example of comprehensive identification of the top and bottom boundaries of carbonate karst erosion in Well Y (drilling, core, logging); Figure 3 Example of depth versus dissolution porosity curves calculated for three single wells with three different unconformity contact relationships; Figure 4 Example diagram of karst zone delineation in the overburden area based on single-well constraints and seismic inversion results. Detailed Implementation

[0008] The following example, using a specific buried hill in the G-depression low uplift, further illustrates the effectiveness of the invention. The specific steps for characterizing the alteration of carbonate reservoirs in rift basins by tectonic movements are as follows (…). Figure 1 ): S1. Four-point calibration in the adjacent outcrop area determines the key structural motion response characteristics. S11. For the outcrop area around G depression, select four standard points (A, B, C, D) with good outcrop conditions, continuous strata and clear structure. Establish a complete longitudinal column of carbonate reservoir based on the four standard points to clarify its sequence, lithology and structural interface. Extend and connect the four standard points respectively to construct four typical regional two-dimensional stratigraphic profiles (i.e. "four points and four beams") based on the four standard columns, forming an outcrop correlation framework of different tectonic-sedimentary facies zones in the covered area. S12. For the four standard columns, the key tectonic movement interfaces (unconformities and fault zones) were systematically identified, and their corresponding dissolution characteristics (including dissolution caves, dissolution pores, and dissolution fracture types) and infill types were identified, especially the infill breccia and its arrangement. Vertical dissolution zones were divided, and the number of fractures, the porosity, and the proportion of dissolution zones were statistically analyzed based on the depth of each zone from the top boundary, and a longitudinal distribution pattern of karst zones in the outcrop area was established (Table 1). Table 1. Statistics of vertical seepage zones at the top of the Ordovician strata in the Carboniferous-Ordovician discontinuity of the key pillars in the northern section. Zoning Distance from top width / m Main types of corrosion Number of cracks Pore ​​ratio Overall percentage of the dissolution zone / % Strong dissolution zone 13.8 Caves and fissures 15 4.7 55.8 intermediate dissolution zone 41.3 Solvation 6 2.8 33.3 Weak dissolution zone 64.9 A small amount of interstitial spaces and pores — 0.92 10.9 extremely weak dissolution zone 37.2 A small number of dissolution pores — — 0 (3) Based on the comparison results of the four profiles, the differences in the characteristics of dissolution development in different key tectonic periods were clarified, and the model of the formation, modification and filling of carbonate rock dissolution space by different tectonic movements was established to quantify its karst development model. For a single tectonic-karst event, the relationship between the intensity and depth of dissolution can be expressed by the following function: Yi(X) = aiX4 + biX3 + ciX2 + diX + ei Where Yi is the dissolution width generated by the tectonic movement in the i-th phase; X is the vertical depth from the unconformity interface in the i-th phase; ai, bi, ci are the higher-order coefficients controlling the shape of the erosion curve; di is the core coefficient controlling the linear trend of the curve; and ei is the curve intercept or reference term. S2. Multi-information delineation of tectonic karst interfaces and extent in the study area S21. Based on the karst zone distribution model established in the outcrop area, the top and bottom boundaries of carbonate rock strata are determined by combining core, logging and well logging methods, and the lithology and contact relationship of the overlying strata are clarified; the internal strata of carbonate rocks are subdivided by combining the cyclic stratigraphy method to establish a high-resolution stratigraphic framework. S22. Based on well venting, well kick (blowout), and well leakage during the drilling process, the karst zone is initially identified. Based on the core samples depicting dissolution pores, caves, and fractures, and after correcting physical property logging (sonic, neutron, and density logging) and FMI imaging logging, a multi-information fusion method is formed, which uses "drilling response to locate the karst zone, core samples to depict the karst zone, and logging response to calibrate the boundaries of the top and bottom of the karst zone" to identify and calibrate the dissolution development zones related to key tectonic movement interfaces. like Figure 2 As shown, the porosity calculated by acoustic, neutron and density logging is corrected based on the porosity on the core. The paleosol on the key unconformity interface is used as the reference surface. Based on the well leakage, core dissolution etching, and related physical property logging curves, a relationship curve between depth and dissolution porosity increment is established with the unconformity reference surface as the boundary. S3. Quantitative analysis of the constraints of different tectonic movements on carbonate reservoirs at single well points. S31. Using "overlying strata constraint" as the standard, key unconformities between the overlying strata and the target carbonate rock layers in the study area were screened out (i.e., unconformities of the Carboniferous-Ordovician discontinuity corresponding to the Caledonian orogeny, the Jurassic-Ordovician discontinuity corresponding to the Hercynian-Indosinian orogeny, and the Paleogene-Ordovician discontinuity corresponding to the Yanshanian orogeny). S32. For wells drilled through carbonate rocks (such as low uplifts) in the study area, a "gradual reduction" method was adopted to strip and quantify the degree of dissolution of carbonate reservoirs by different tectonic movements and cumulative tectonic movements. Figure 3 The specific steps are as follows: S321. Based on the top of the Ordovician system, first determine the depth of the dissolution zone and its dissolution envelope of the Caledonian Movement (Carboniferous-Ordovician discontinuity); S322. Determine the depth and envelope of the dissolution zone of the Hercynian-Indosinian orogeny (Jurassic-Ordovician discontinuity). Subtract the Caledonian orogeny dissolution portion already included in step 1. This is the degree of new dissolution modification of the Ordovician system by the Hercynian-Indosinian orogeny. S323. Determine the depth and envelope of the dissolution zone of the Yanshan Movement (Paleogene-Ordovician discontinuity); subtract the dissolution contributions from steps 1 and 2 in sequence, and the remaining part is the degree of new dissolution modification of the Ordovician system by the Yanshan Movement. Based on the above stripping analysis, a relationship model with the corrosion width and the depth of the corrosion zone from the unconformity as variables is established to quantitatively characterize the independent and cumulative corrosion influence ranges of each stage of movement; Calculation of cumulative corrosion effect: As of the Nth stage of tectonic movement, the cumulative total corrosion effect (Y independent(X) , , , , Tectonic movement Independent Dissolution Depth Caledonian Movement Maximum Cumulative Dissolution Depth Maximum cumulative dissolution depth of the Caledonian-Hercy-Indosinian Movement Caledonian Movement 0～197m 0 0 Haixi-Indochina Movement 110～220m 263m 0 Yanshan Movement 220～305m — 424m , , , , , well location Total thickness / m Caledonian motion thickness / m Haixi-Indosinian Movement thickness / m Yanshan Movement Thickness / m Z10 126 126 — — ZG5 130 130 — — Z8 115 115 — — Z30 130 130 — — ZG1 142 142 — — ZG22 113 113 — — Z7 194 126 68 — Z18 203 126 77 — Z24 189 126 63 — Z55 211 126 85 — ZG1 218 126 92 — ZG101 207 126 81 — ZG45 293.6 126 77.6 90 Z6 287.6 126 77.6 84 Z53 293.6 126 77.6 90 ZG1-1 313.6 126 77.6 110 ZG20 315.6 126 77.6 112 ZG3 300.6 126 77.6 97 average thickness 126 77.6 97.1 , ,

[0010] , ) suffered by the carbonate rock is approximately expressed as the superposition of the independent effects of each stage within the effective depth range: Y total(X) ≈ Among them, X In the calculations of each stage, it is calculated starting from its own unconformity surface; Stripping of independent corrosion contribution (implemented by the "layer-by-layer decreasing" method): To strip out the independent new corrosion contribution (Yi independent（X） ) of the ith stage of tectonic movement, it is necessary to deduct the corrosion contributions already generated at this place by all older stages (j < i) of tectonic movement from the cumulative corrosion characteristics observed below the unconformity surface of this stage: Yi independent(X) = Yi cumulative(X) −

[0009] Among them, Yi independent(X) is the independent new corrosion width generated by the ith stage of tectonic movement, characterizing the influence range of the corrosion intensity in the horizontal direction; i is the serial number of the tectonic movement stage; X is the vertical depth from the ith-stage unconformity interface; is the jth stage of tectonic movement older than the ith stage of tectonic movement; Table 2 Data table of the calculated corrosion depth of a single well in a certain block Tectonic movement Independent Dissolution Depth Caledonian Movement Maximum Cumulative Dissolution Depth Maximum cumulative dissolution depth of the Caledonian-Hercy-Indosinian Movement Caledonian Movement 0～197m 0 0 Haixi-Indochina Movement 110～220m 263m 0 Yanshan Movement 220～305m — 424m S4. Construct the tectonic evolution process of the trinity carbonate reservoir reconstruction The "trinity" comprehensive analysis method realizes the quantitative restoration of the corrosion and reconstruction of the carbonate reservoir by multi-stage tectonic movements, that is, "point" determines the thickness of the corrosion zone of different tectonic movements through single-well statistics, and in the area without wells, the three-dimensional spatial distribution of the corrosion zone is determined through seismic inversion. "Surface" determines the trend line of the thickness change of the corrosion zone of different tectonic movements by the gradually decreasing method, and then realizes the evolution process of the tectonic movement on the carbonate reservoir reconstruction.

[0010] S41. Based on the single-well point, the wells with the same unconformity contact relationship on the same tectonic block are statistically analyzed respectively, and the interval values of the reconstruction of the carbonate reservoir by different tectonic movements are statistically calculated; Table 3 Statistical table of the corrosion thickness corresponding to different tectonic movements in the Z fault block area well location Total thickness / m Caledonian motion thickness / m Haixi-Indosinian Movement thickness / m Yanshan Movement Thickness / m Z10 126 126 — — ZG5 130 130 — — Z8 115 115 — — Z30 130 130 — — ZG1 142 142 — — ZG22 113 113 — — Z7 194 126 68 — Z18 203 126 77 — Z24 189 126 63 — Z55 211 126 85 — ZG1 218 126 92 — ZG101 207 126 81 — ZG45 293.6 126 77.6 90 Z6 287.6 126 77.6 84 Z53 293.6 126 77.6 90 ZG1-1 313.6 126 77.6 110 ZG20 315.6 126 77.6 112 ZG3 300.6 126 77.6 97 average thickness 126 77.6 97.1 S42. Using the single-well dissolution range on the structural block as a benchmark, the regional control erosion depth line determined by S1 as a constraint, and the inversion results of the seismic waveform indicator inversion method as the core, the distribution of the dissolution zone in three-dimensional space is constructed, such as... Figure 4 ; S43. The influence of early tectonic movements was eliminated in sequence, as shown in Table 3. Combining the idea of ​​"four points and four beams" guiding the center point of the outcrop area, the dissolution process of carbonate reservoirs under different tectonic movements was restored.

Claims

1. A method for characterizing the effect of tectonic movement on the dissolution evolution of carbonate reservoirs in rift basins, characterized in that, Includes the following steps: S1. Four-point calibration in adjacent outcrop areas: In the outcrop areas adjacent to the study area, select at least four standard points to establish a columnar section of carbonate rock strata, and expand it into multiple two-dimensional stratigraphic sections; identify the key tectonic movement interfaces in the sections, describe their related dissolution and filling characteristics, and establish the vertical distribution pattern of karst in the outcrop areas. S2. Multi-information delineation of the study area: Based on the outcrop model, the sequence framework of the underground carbonate strata is determined by integrating core, logging and well logging data; the key tectonic movement interfaces and related karst development zones are identified and marked by a combination of drilling response, core characterization and well logging response methods. S3. Quantitative Constraints for Single Wells: Screening the interfaces of multiple key tectonic movements overlying the target carbonate rock layer; for single wells, a layer-by-layer decreasing quantitative analysis method is used to determine the range of the dissolution zone formed by each tectonic movement in turn, and the independent dissolution contribution of each tectonic movement is calculated by subtracting the contribution of older periods from the cumulative dissolution effect. S4. The three-in-one construction of the evolution process: Based on the quantitative data of dissolution at single well points in stages, combined with the three-dimensional distribution of dissolution zones characterized by seismic inversion, the history of dissolution and transformation of reservoirs by tectonic movements in each stage is restored by successively eliminating the influence of newer tectonic movements.

2. The method according to claim 1, characterized in that, In step S4, the relationship between the dissolution intensity and depth resulting from the single-stage tectonic-karst event can be expressed by the following formula: Yi(X) = aiX4 + biX3 + ciX2 + diX + ei Where Yi is the dissolution width generated by the tectonic movement in the i-th phase; X is the vertical depth from the unconformity interface in the i-th phase; ai, bi, ci are the higher-order coefficients controlling the shape of the erosion curve; di is the core coefficient controlling the linear trend of the curve; and ei is the curve intercept or reference term.

3. The method according to claim 1, characterized in that, In step S3, the layer-by-layer decreasing quantitative analysis method is as follows: For a single well with N key tectonic movement interfaces, firstly, the range of the dissolution zone formed by the first phase of movement is defined; then, the range of the dissolution zone formed by the second phase of movement is defined, and the contribution of the first phase is subtracted from it to obtain the independent dissolution contribution of the second phase of movement; this process is repeated until the calculation of the independent dissolution contribution of the Nth phase of movement is completed, calculated using the following formula: Yi independent(X) =Yi cumulative(X) - Among them, Yi independent(X) X represents the independently added dissolution width generated by the i-th tectonic movement, characterizing the lateral influence range of the dissolution intensity; i is the tectonic movement period number; X is the vertical depth from the i-th unconformity interface; It is the j-th tectonic movement, which is older than the i-th tectonic movement.

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