Quantitative analysis technology for material source supply of delta transformation type beach bar

Abstract

The invention discloses a material source supply quantitative analysis technology for a delta transformation type beach bar. The technology comprises the following steps: (1) determining beach bar development through rock core-well logging-earthquake; (2) qualitatively analyzing a delta-beach and bar material source system; (3) material source parameter selection and quantitative calculation; and (4) establishing an analysis model based on an AHP theory. The beach bar development well position is obtained based on core, slice and logging data, and the beach bar development position, range and deposition mode are determined in combination with seismic data; zircon dating is combined with a sand thickness ratio and maturity contour map to qualitatively analyze the direction of an object source region; the paleo-flow field is recovered based on the BPT technology, the paleo-flow velocity and the paleo-flow direction are obtained, and flow field data, the transmission distance, the source supply capacity of the material source area and the length of the material source area are selected as influence parameters; and determining an influence factor weight of each influence parameter based on an AHP model, performing consistency check, and establishing a quantitative analysis model through post-weighted stacking. According to the method, quantitative analysis of the beach and bar provenance area is completed for the first time, and important reference is provided for a more perfect provenance analysis system in geological research.

Description

Technical Field

[0001] The invention provides a quantitative analysis technology for the material supply of delta-transformed beach-bars, and belongs to the technical fields of sedimentology, data processing and model building. Background Art

[0002] Sediment provenance analysis is an important aspect of basin analysis, and has important guiding significance for the evolution of sedimentary basins and the restoration of paleoenvironment. In the early days, traditional provenance analysis methods focused on qualitative analysis, such as detrital component analysis, detrital zircon dating, and rubidium strontium isotope dating. At present, provenance analysis has gradually become quantitative and developed into two branches: one is pattern discrimination, such as fuzzy clustering and neural network recognition; the other is to achieve quantitative provenance analysis based on the principle of "mass conservation" through mathematical and statistical methods.

[0003] However, in actual research, the current quantitative analysis methods have many problems. The first is the limitation of the analysis system. Most scholars have considered the type, quantity and supply rate of materials from the provenance area to the basin filling process, ignoring the source of sedimentary materials and the distribution ratio of different provenance areas. The second is that the quantitative analysis technology lacks pertinence. Different sedimentary phases have obvious differences in source supply patterns. They can be directly supplied by water systems or uplifts, or formed by secondary transformation of other sedimentary systems. It is no longer appropriate to use only traditional methods. Based on the above reasons, this patent proposes a quantitative analysis technology for the source supply of delta-transformed beach bars.

[0004] This technology uses basic core, logging and seismic data, based on the AHP theory, to innovatively realize quantitative analysis of the provenance of delta-transformed beach-bars. This method can fully consider the source and proportion of sediments and is targeted, providing support for the improvement of the beach-bar provenance analysis system and the exploration of favorable closures. Summary of the invention

[0005] The purpose of the present invention is to provide a quantitative analysis technology for the material supply of delta-transformed beach-bars, aiming to solve the problem of quantitative analysis of the material supply of beach-bars.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for quantitatively restoring the material supply of a delta-transformed beach bar, which comprises the following steps:

[0008] Step 1: “core-logging-seismic” to determine the beach-bar development;

[0009] Step 2: Qualitative analysis of delta-beach-bar provenance system;

[0010] Step 3, source parameter selection and quantitative calculation;

[0011] Step 4: Establish an analysis model based on AHP theory;

[0012] According to the above scheme, step 1 specifically includes the following sub-steps:

[0013] Step 1.1: Core observation;

[0014] Step 1.2: Well logging feature identification;

[0015] Step 1.3: Earthquake feature identification.

[0016] In the step 1.1, core observation, first select key coring wells for macroscopic observation, and preliminarily determine the development location of the beach bar. The beach bar core has the following characteristics: First, it is an anti-cyclic sequence as a whole. Within a complete first-stage beach bar, as the depth becomes shallower, the grain size gradually increases, and the lithology also transitions from siltstone to medium-coarse sandstone; second, the sandstone layer of the beach bar is obviously thinner, and the thickness of the complete first-stage sedimentation is also small, generally about 2 meters thick per layer; third, the structural characteristics are obvious. The beach bar develops in a coastal shallow lake environment and is repeatedly transformed by waves and coastal currents, mainly showing characteristics such as wave-formed sand ripple bedding, washed cross-bedding, and large-scale wavy cross-bedding. After the core is placed correctly, first observe the whole body to find obvious lithology changes, such as lithology mutations, grain sequence, color changes, etc., and preliminarily identify the beach bar stage based on this. Then, observe and record each piece in detail, including lithology, color, grain size, bedding, sedimentary structure and other characteristics, and pay attention to oil immersion and the presence or absence of biological debris. According to the above process, the preliminary identification of the beach bar is completed in terms of the core;

[0017] In the step 1.2, logging characteristics are identified, and the logging data of key coring wells and surrounding wells are sorted and analyzed, mainly including lithology channels, logging curve channels (GR, AC, SP, etc.). The identification of beach and bar in logging mainly includes the following characteristics: due to repeated water flow scouring and transformation, the sandstone layer of the beach and bar lithology channel has obvious anti-cyclic characteristics, and the logging curve morphology is mainly funnel-shaped and finger-shaped, with a high amplitude and micro-toothing. At the same time, it is necessary to focus on the mutual verification of the lithology data on the logging and the core observation results. Based on the above content, beach and bar identification can be completed on the logging;

[0018] In step 1.3, the seismic characteristics analysis should comprehensively consider the well logging and core data, clarify the well location of beach-bar development, and preliminarily identify the beach-bar development point in the study area. Beach-bars show short-axis discontinuity and complex wave reflection characteristics on the seismic profile, and the frequency is low. Taking the beach-bar development point as the base point, the scope of the beach-bar is further characterized by intercepting seismic profiles and attribute maps in different directions. Based on the above content, the development location and scale of the beach-bar can be determined.

[0019] According to the above scheme, step 2 specifically includes the following sub-steps:

[0020] Step 2.1: Zircon dating and provenance tracing;

[0021] Step 2.2: sand-soil ratio and maturity analysis;

[0022] In step 2.1, zircon dating and provenance tracing are carried out. Sandstone core samples are selected from the wells with beach-bar development, crushed and acid-etched in the laboratory, and zircon grains in the samples are observed using a binocular optical microscope. Grains with better crystal shape are selected to make zircon targets. Cathodoluminescence (CL) microscopic images can be taken and U-Pb chronology analysis can be performed. Provenance tracing is carried out based on characteristics such as crystal grain size, columnar characteristics, angular morphology, and U-Pb image peaks.

[0023] In step 2.2, sand-to-formation ratio and maturity analysis, sandstone thickness and formation thickness are statistically analyzed through well logging data; quartz, feldspar and debris content are obtained through experimental statistics, and the sand-to-formation ratio and composition maturity values ​​of each point can be calculated through the formula. After Kriging interpolation, contour maps are drawn, and the qualitative analysis of the beach-bar source area is completed in combination with zircon dating.

[0024] According to the above scheme, step 3 specifically includes the following sub-steps:

[0025] Step 3.1: Selection of quantitative parameters of provenance;

[0026] Step 3.2: Quantitative restoration of paleoflow field;

[0027] Step 3.3: Quantitative calculation of other parameters.

[0028] In step 3.1, the quantitative parameters of provenance are selected. On the basis of the identification of beach-bar morphology and development location, the genetic pattern of the beach-bar is comprehensively analyzed, and the paleocurrent field, the diameter of the provenance area, the transport distance, and the source supply capacity of the provenance area are selected as the influencing factors for quantitative identification of provenance;

[0029] In step 3.2, the paleoflow field is quantitatively restored, and the flow velocity and flow direction can indirectly reflect the amount of flow, that is, the ability of the water flow to carry materials in the source area. The BPT technology was proposed by Adams. Based on the solitary wave theory, it considers the relationship between the unidirectional water flow carrying capacity and the sediment characteristics, and can calculate the critical wave conditions for transporting sediment particles. This technology is mainly used for the calculation of flow field and paleowind speed. This technology is the first to use flow velocity as the main factor for quantitative source analysis and apply it to quantitative source restoration. The main formula is as follows (according to Adams, 2004):

[0030] When the sediment starts to start, the critical shear force generated by the flowing water on the sediment surface is:

[0031]

[0032] Among them, ρ wis the density of water medium, D B is the median particle size of the sediment, D m is the maximum particle size, and g is the acceleration due to gravity.

[0033] The critical shear stress obtained needs to be corrected ( Figure 2 ):

[0034]

[0035] Among them, β is the slope of the beach bar, is the particle rotation angle, which can be obtained by the following formula:

[0036]

[0037] Convert the critical shear force to the critical friction velocity for transporting this particle along the bed surface:

[0038]

[0039] The critical friction velocity can be converted into the velocity profile of the fluid medium (according to Adams),

[0040] u z =5.75u *c log(30z / k s )

[0041] Among them, u z is the flow velocity at a distance z above the bed bottom; k s is the roughness, k s =δD 50 , δ is the bottom bed roughness coefficient;

[0042] The flow direction can refer to the survey results in paleometeorology, and then the projection of the flow velocity on the connecting line between the center of the beach bar and the center of the source area is taken as the effective flow velocity, which is used in the subsequent model construction;

[0043] In the step 3.3, other parameters are quantitatively calculated: ① The diameter of the provenance area. The maximum diameter passing through the center of the provenance area reflects the size of the provenance area itself, that is, the maximum amount of provenance that can be provided; ② Transportation distance. The longer the transportation distance between the center of the provenance area and the center of the beach bar, the greater the loss, and the less material may be provided for the later beach bar deposition. ③ Supply capacity. Different types of provenance areas contain different mineral components, and the degree of erosion is also different. The average firmness coefficient is used to characterize the weathering resistance of rocks. In the quantitative restoration of provenance, it is used as an influencing parameter for the first time. The larger the average firmness coefficient, the stronger the rock's resistance to weathering and erosion, and the relatively weaker the supply capacity, as shown in Table 1.

[0044] Table 1 Average strength coefficient of various types of rocks

[0045]

[0046] According to the above scheme, step 4 specifically includes the following sub-steps:

[0047] Step 4.1: Data preprocessing;

[0048] Step 4.2: Construct a judgment matrix;

[0049] Step 4.3: Weight calculation;

[0050] Step 4.4: Model construction.

[0051] In step 4.1, data preprocessing, the source area diameter and effective flow rate are extremely large indicators, and the average solidity coefficient and transportation distance are extremely small indicators. It is necessary to positively and standardize the parameter factor indicators to obtain the source area diameter S, transportation distance L, source supply capacity W, and effective flow rate V;

[0052] In step 4.2, a judgment matrix is ​​constructed, and a suitable scale is determined by comparing each influencing parameter pairwise. The judgment matrix can be established by combining the expert scoring results with the 1-5 point scale method (or 1-9 point scale method, see Table 2);

[0053] Table 21-9 Meaning of the scale method

[0054]

[0055] In step 4.3, weight calculation, AHP model is a traditional evaluation model. This technology applies its weight calculation process for the first time to score the influencing factors of each material source to prepare for model construction*. Among them, there are many weight calculation methods, including eigenvalue method, geometric mean method, arithmetic mean method, etc., and the best method can be selected by comprehensive comparison. After calculating the final weight, the consistency test mainly includes the consistency index CI and the consistency ratio CR. If the two tests pass, the normalized eigenvector is the weight vector; if not, the judgment matrix calculation is reconstructed.

[0056] In step 4.4, the model is constructed, assuming that a certain beach-bar deposition is controlled by three provenance areas A, B, and C. If it is finally determined, the weight value of the provenance area length is a, the weight value of the transport distance is b, the weight value of the effective flow velocity is c, and the weight value of the source capacity is d; for the flow velocity: V A :V B :V C =V1:V2:V3; for conveying distance: L A :L B :L C =L1:L2:L3; for the source area diameter: S A :S B :SC =S1:S2:S3; For the source area supply capacity: W A :W B :W C =W1:W2:W3, then the source supply capacity Q of provenance areas A, B, and C is:

[0057] Q A =a·S1+b·L1+c·V1+d·W1

[0058] Q B =a·S2+b·L2+c·V2+d·W2

[0059] Q C =a·S3+b·L3+c·V3+d·W3

[0060] The source ratio of provenance areas A, B, and C is Q A :Q B :Q C According to the depicted beach-bar volume, the supply of each provenance area can be calculated proportionally.

[0061] Based on the AHP model, combined with core observation, logging, seismic profile data and other methods, we went a step further on the basis of previous qualitative analysis of the provenance area and selected data on transportation distance, provenance area length, flow field, and source supply capacity of the provenance area to solve the problem of quantitative identification of beach-bar provenance. At the same time, combined with the actual research, we analyzed a method of ancient flow field restoration, which provided guidance for further improving the beach-bar sedimentary model and the exploration and development of beach-bar oil and gas reservoirs in my country. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0063] Figure 1 is a flow chart of the method provided by the present invention;

[0064] Figure 2 It is a schematic diagram of shear force correction in paleoflow field restoration provided by the present invention;

[0065] Figure 3 A schematic diagram of core feature identification provided in Example 1 of the present invention;

[0066] Figure 4 A schematic diagram of well logging feature recognition provided in Example 1 of the present invention;

[0067] Figure 5 is a schematic diagram of seismic profile feature identification provided by Example 1 of the present invention;

[0068] Figure 6 It is a schematic diagram of the maturity and sand-to-land ratio contour map provided in Example 1 of the present invention;

[0069] Figure 7 This is a schematic diagram of parameter acquisition provided by Embodiment 1 of the present invention;

[0070] Figure 8 This is a schematic diagram of model construction provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0071] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0072] The early sedimentary facies of the Liaodong Bay Luda A structural area were all fan delta systems. At present, core logging and seismic analysis show that the block also has beach-bar deposits. We used the above-mentioned "quantitative analysis technology of the source supply of delta-transformed beach-bars" to complete the quantitative discrimination of the source area's supply ratio of the beach-bar deposits in the Liaodong Bay Depression Luda A structural area for the first time.

[0073] like Figure 1 As shown, a quantitative analysis technology for the source supply of delta-transformed beach-bars includes the following steps:

[0074] 1. Determination of the location of beach-bar development in the Luda A structural area;

[0075] (1) Core observation. The beach-bar sedimentary characteristics are obvious, with inverse grain sequence and typical bedding structure on the core, such as Figure 3 As shown, it includes wavy bedding, wave-shaped sand ripple bedding, climbing sand ripple bedding, etc. The lithology is mostly gray fine sandstone, and the sandstone layer is relatively thin, which meets the beach bar core identification standard.

[0076] (2) Well logging analysis. Figure 4 As shown in the figure, the beach-bar logging curve is funnel-shaped, with anti-cyclic characteristics and typical beach-bar response. The lithology track shows that from bottom to top, the lithology transitions from muddy siltstone to fine sandstone, and the sandstone layer is relatively thin, which can be identified as a beach-bar development point on the logging.

[0077] (3) Seismic profile analysis. Figure 5 As shown in the figure, on the seismic section, the short axis is discontinuous and the frequency is low, and the shape is hilly, which meets the criteria for distinguishing beach-bar seismic phases.

[0078] 2. Qualitative analysis of the provenance system of the Luda A tectonic area

[0079] The sediments from several wells in the Luda A structural area are all magmatic zircons. The zircon crystals in the samples are large and have obvious columnar characteristics. Most of the crystals are intact and have clear edges and corners, which are characteristics of near-source sedimentation. Figure 6As shown in the figure, from the fan delta development point to the beach-bar development point, the sand-to-land ratio and the contour value increase, indicating that the provenance direction is from the fan delta front to the beach-bar point.

[0080] 3. Calculation of influencing parameters of provenance analysis in the Luda A structural area;

[0081] like Figure 6 , 7 As shown, paleoflow field data, transport distance, provenance area diameter, and provenance area supply capacity were selected as influencing factors to participate in the later model construction.

[0082] (1) Calculation of paleoflow field. The beach-bar source area of ​​the Luda A structural area, i.e., the northeastern fan delta, is divided into three sedimentary systems, namely A, B, and C. Grain size data is obtained through core data; slope data is obtained based on the existing paleo-geomorphological restoration results; water particle density and gravity acceleration are empirical values. After calculation, the flow velocity near the source area A is 0.174 m / s, the flow velocity near the source area B is 0.205 m / s, and the flow velocity near the source area C is 0.231 m / s. The obtained flow velocity data is converted into projections on the three source blocks and the beach-bar connecting line to obtain effective flow velocities, which are 0.168 m / s, 0.201 m / s, and 0.225 m / s, respectively.

[0083] (2) Calculation of other parameters. The transport distance is the distance between the center points of the three provenance areas, which can be calculated proportionally according to the scale in the figure. After analysis, the distances between provenance areas A, B, and C and the center point of the beach bar are 5 km, 9.5 km, and 17 km, respectively. The diameter of the provenance area is similar to the transport distance, and the diameters of provenance areas A, B, and C are 10 km, 7.5 km, and 8 km, respectively; the source capacity is expressed by the solidity coefficient. Since the three provenance areas are all fan delta deposits with similar lithological compositions, the value is 8.

[0084] 4. Construct a quantitative analysis model of material provenance;

[0085] (1) Data positive and normalization processing results. See Table 3:

[0086] Table 3 Data processing results

[0087]

[0088] (2) After expert scoring, a judgment matrix is ​​constructed. See Table 4:

[0089] Table 4 Construction of judgment matrix

[0090]

[0091]

[0092] After calculation, a=0.1, b=0.16; c=0.27, d=0.47, CI=0.0105, CR=0.0093, the test passed.

[0093] (3) Establish a quantitative analysis model;

[0094] After calculation, Q A =0.569, Q B =0.551, Q C =0.541

[0095] Q A :Q B :Q C =569:551:541

[0096] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A quantitative analysis technology for the source supply of delta-transformed beach-bars, characterized in that Based on AHP theory and combined with geological data, the quantitative identification problem of beach-bar source supply was solved, including the following steps: (1) "Core-logging-seismic" to determine beach-bar development; (2) Qualitative analysis of the delta-beach-bar provenance system; (3) Selection and quantitative calculation of provenance parameters; (4) Establish an analysis model based on AHP theory.

2. The quantitative analysis technology of the source supply of delta-transformed beach-bar according to claim 1 is characterized in that: In step 1, firstly, the key coring wells are selected, and the macro-micro combination method is adopted. The core sequence is drawn macroscopically to observe the overall characteristics of the core, including sandstone thickness, lithology changes, sedimentary structure, etc., and further identified by combining thin sections and grain size data microscopically; secondly, the logging curve sequence of the thicker sandstone section (greater than 2m) is extracted, and the well location of the beach-bar sand body development is determined according to the logging curve morphology and value range; finally, the seismic profile is intercepted, the attribute value is extracted, and the development position and range of the beach-bar are described.

3. The quantitative analysis technology of the source supply of delta-transformed beach-bar according to claim 1 is characterized in that: In step 2, for the beach-bar well locations, the mudstone section is first eliminated, and sandstone cuttings are sampled for detrital zircon U-Pb dating analysis. The provenance is traced through Th / U ratio diagrams, zircon U-Pb age spectra, zircon CL images, etc., and the delta-beach-bar provenance system is qualitatively analyzed in combination with sandstone thickness contour maps and maturity maps.

4. The quantitative analysis technology for the source supply of delta-transformed beach-bar according to claim 1 is characterized in that: In step 3, the depositional pattern of beach-bar sand bodies is comprehensively considered, and it is believed that the paleoflow field (paleovelocity V, paleoflow direction), transportation distance L, length of the provenance area S and the source supply capacity W (average solidity coefficient) of the provenance area itself have a significant control effect on the beach-bar source supply. Therefore, the present invention innovatively selects the above parameters as influencing factors to complete the construction of a quantitative discrimination model for beach-bar provenance. In this step, the BPT technology is also used to complete the restoration of the paleoflow field, providing theoretical guidance for the later exploration of beach-bar sand bodies.

5. The quantitative analysis technology of material supply of delta-transformed beach-bar according to claim 1 is characterized in that: In step 4, the obtained parameter data are first preprocessed. The flow field data and the length of the provenance area are extremely large indicators and can be standardized. The transportation distance and the source supply capacity of the provenance area (average solidity coefficient) are extremely small indicators and need to be positively converted. Secondly, based on the AHP theory, the expert scoring results are obtained. According to the importance of different factors, a judgment matrix is ​​constructed to calculate the weights of the provenance influencing factors and perform a consistency test. Finally, the principle of weighted superposition is used to innovatively construct a quantitative discrimination model for beach-bar provenance, and the control intensity of the selected factors on the beach-bar sand body under different influence weights is obtained, thereby obtaining the proportion of the supply of each provenance area to the beach-bar source. Combined with the depicted beach-bar volume, the supply of each provenance area can also be calculated.

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