Reservoir quality prediction method for deep and old layer series based on "top-slope-depression" superimposition process analysis

Abstract

The application provides a reservoir quality prediction method based on a "top-slope-depression" superimposition process analysis, and relates to the technical field of oil and natural gas exploration and development; including the following steps: S1, analyzing the present structural characteristics of a target reservoir according to seismic data; S2, restoring a balanced profile, and analyzing the structural evolution process experienced by the reservoir since deposition; S3, analyzing the open and closed evolution processes of the reservoir diagenetic geochemical system according to the "top-slope-depression" superimposition process of the reservoir; S4, determining the diagenesis under different geochemical systems; S5, reservoir quality classification evaluation and spatial distribution prediction. The application uses seismic data to analyze the information of unconformity, overlying strata, burial depth and the like, analyzes the structural / geochemical system evolution process, predicts the distribution law of reservoirs of different levels, and solves the problems of reservoir distribution and pre-drilling prediction under the background of multi-period structural superimposition of deep old layer series.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development technology, specifically to a reservoir quality prediction method based on the analysis of the "top-slope-depression" superposition process. Background Technology

[0002] Reservoirs are underground oil and gas accumulation sites, and reservoir quality is a crucial factor restricting deep oil and gas exploration. After the deposition of primordial clastic material, it consolidates into rocks during burial, undergoing different diagenetic processes that reduce or increase rock properties. With the increasing exploration of shallow and medium-depth oil and gas and the growing demand for increased oil and gas reserves, exploration targets have gradually shifted to deep ancient strata. my country's deep ancient strata possess enormous oil and gas resource potential, and exploration has yielded encouraging results. Deep ancient strata reservoirs often undergo multiple phases of tectonic uplift and subsidence. Due to the complexity of stratigraphic evolution, reservoirs experience various geochemical systems during burial, and the differences in reservoir evolution processes under the same sedimentary background lead to significant variations in reservoir quality. The complexity of the spatial distribution of reservoirs of different qualities is a major reason for the complex oil and gas enrichment patterns and low exploration success rate in deep ancient strata. Therefore, accurately predicting the reservoir quality and distribution in deep ancient strata under complex tectonic backgrounds is of great significance for studying oil and gas migration and accumulation.

[0003] Previous techniques have primarily targeted shallow and intermediate-level strata, requiring diagenetic analysis of borehole cores or a combination of core and logging data for detailed analysis, thus demanding high-quality geological data. Therefore, new technologies are needed to predict the quality of deep, ancient reservoir strata before drilling, especially when evolutionary processes are complex and geological data is scarce. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a reservoir quality prediction method based on the analysis of the "top-slope-depression" superposition process, which solves the problem of pre-drilling prediction of the quality of deep ancient strata reservoirs when the evolution process is complex and geological data is scarce.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a reservoir quality prediction method based on the analysis of the "top-slope-depression" superposition process, comprising the following steps:

[0008] S1. Based on seismic data, analyze the current structural characteristics of the target reservoir;

[0009] S2. Restore the equilibrium profile and analyze the tectonic evolution process that the reservoir has undergone since its deposition.

[0010] S3. Based on the reservoir's "top-slope-depression" superposition process, analyze the evolution of the reservoir's diagenetic system;

[0011] S4. Determine the diagenesis and its reservoir-forming effects under different diagenetic systems;

[0012] S5. Reservoir quality classification and evaluation and spatial distribution prediction;

[0013] The reservoir is divided into the following categories according to the steps described above:

[0014] Type I reservoir: Under conditions of multiple uplifts and lack of deep burial, it remains in an open system for a long period of time;

[0015] Type II reservoirs: Under the conditions of early uplift and late intermediate-deep burial, the reservoirs experience an early-opening-late-closing system;

[0016] Type III reservoirs: Reservoirs that have not been uplifted to the surface and have been buried at medium to deep depths for a long time are in a closed diagenetic system.

[0017] Preferably, the current structural characteristics of the target reservoir analyzed in S1 include: unconformity development above the reservoir, overlying strata, and current burial depth;

[0018] The current structural features are divided into three categories: 1. Regional unconformities are developed above the reservoir, with a large number of overlying strata missing, and the reservoir is currently shallow; 2. Small-scale unconformities are developed above the reservoir, with some overlying strata missing, and the reservoir is currently deeply buried; 3. There are no angular unconformities above the reservoir, with the overlying strata intact, and the reservoir is currently deeply buried.

[0019] Preferably, in S3, when the strata are uplifted to the surface or near the surface, the reservoir is in an open diagenetic system; during the burial process of the strata, the reservoir is in a closed diagenetic system.

[0020] Preferably, in the "top-slope-depression" superposition process in S4, the open diagenetic system has strong dissolution and weak precipitation, and the diagenetic process as a whole increases porosity and improves permeability, resulting in better reservoir quality. In the closed diagenetic system, while dissolving and forming pores, strong cementation and precipitation occur, and the diagenetic process cannot improve reservoir quality. Therefore, the reservoir quality can be predicted by the "top-slope-depression" superposition of the reservoir during the evolution process.

[0021] (III) Beneficial Effects

[0022] This invention provides a reservoir quality prediction method based on the analysis of the "top-slope-depression" superposition process. It has the following beneficial effects:

[0023] This invention utilizes seismic data to analyze information such as unconformities, overlying strata, and burial depth, thereby analyzing the evolution of tectonic / geochemical systems and predicting the distribution patterns of reservoirs at different levels. It solves the problem of reservoir distribution and pre-drilling prediction in the context of multiple phases of tectonic superposition in deep ancient strata, and effectively guides the prediction of reservoir quality in the early stages of oil exploration and development. Attached Figure Description

[0024] Figure 1 A schematic diagram of the "top-slope-depression" superposition process and reservoir prediction of Permian reservoirs in a certain region;

[0025] Figure 2 A schematic diagram of the tectonic and stratigraphic features of a typical region;

[0026] Figure 3 This is a schematic diagram of the dynamic equilibrium profile in a typical region.

[0027] Figure 4 Figure 1 shows the evolution of the reservoir diagenetic system;

[0028] Figure 5 Two figures illustrating the evolution of reservoir diagenetic systems;

[0029] Figure 6 Three figures illustrating the evolution of reservoir diagenetic systems;

[0030] Figure 7 The superposition process of the Permian reservoir in a certain region and the prediction of the reservoir;

[0031] Figure 8 Reservoir quality diagrams under different "top-slope-depression" superposition processes. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1:

[0034] like Figure 1-8 As shown, this invention, based on the identification of current structural features using seismic data, clarifies the "top-slope-depression" superposition process of the reservoir, analyzes the geochemical systems and diagenetic processes experienced by the reservoir, and ultimately predicts the reservoir quality and distribution characteristics. The specific method is as follows:

[0035] First, using seismic data, analyze the current structural characteristics of the target reservoir, including the development of unconformities above the reservoir, overlying strata, and current burial depth. These structural characteristics can be categorized into three types: 1. Regional unconformities develop above the reservoir, with significant gaps in the overlying strata, and the reservoir is currently shallowly buried; 2. Small-scale unconformities develop above the reservoir, with partial gaps in the overlying strata, and the reservoir is currently deeply buried; 3. There are no angular unconformities above the reservoir, with well-preserved overlying strata, and the reservoir is currently deeply buried.

[0036] Second: Restore the equilibrium profile and analyze the tectonic evolution process that the reservoir has undergone since its deposition.

[0037] Third: Based on the "top-slope-depression" superposition process of the reservoir, analyze the evolution process of the reservoir diagenetic system. For the same reservoir at different evolutionary stages or in different tectonic locations (mountain top, slope, deep depression), the "top-slope-depression" superposition process controls the formation of the reservoir. Generally, when strata are uplifted to or near the surface, the reservoir is in an open diagenetic system; during the burial process, the reservoir is in a closed diagenetic system.

[0038] Fourth: Clarify the diagenesis and reservoir formation effects under different diagenetic systems.

[0039] Feldspar minerals are ubiquitous in clastic reservoirs, and feldspar dissolution is the main controlling factor for changes in porosity. Feldspar minerals undergo dissolution under the action of acidic fluids, forming dissolution products such as kaolinite and quartz.

[0040] In open diagenetic systems, large-scale atmospheric water carrying CO2 is injected into the reservoir (mountain top). The fluid flows downward through connected sand bodies, dissolving feldspar minerals extensively in the shallow layers and carrying the dissolution products (kaolinite, quartz) away from the mountain top to form a dissolution zone (increased physical properties). The dissolution products are transported to the slope area or deep depression area for precipitation, successively forming a transition zone (slightly increased physical properties) and a precipitation zone (decreased physical properties). During this process, the reservoir diagenesis varies greatly, resulting in significant differences in reservoir quality.

[0041] In closed diagenetic systems, feldspar dissolution products cannot migrate long distances. Instead, they precipitate in near-in-situ as essentially equal-volume siliceous cement and authigenic kaolinite, having little impact on reservoir porosity. Fifth: Reservoir quality classification and evaluation, and spatial distribution prediction.

[0042] In summary, under the conditions of multiple uplifts and no deep burial, the reservoir in the open system for a long period of time has the best quality and is classified as a Class I reservoir; under the conditions of early uplift and late-term medium-deep burial, the reservoir undergoes an early open-late closed system and has the second best quality and is classified as a Class II reservoir; under the conditions of not being uplifted to the surface and long-term medium-deep burial, the reservoir has not undergone the porosity enhancement process under the open system and has the worst quality and is classified as a Class III reservoir.

[0043] In an open system, the inclined strata develop dissolution zones, transition zones, and sedimentation zones from the top to the bottom, with the reservoir quality deteriorating in that order.

[0044] Therefore, we can conclude that:

[0045] Among the first type of reservoirs, the "early-top-late-top" type reservoir is superior to other superimposed type reservoirs;

[0046] Among the second-class reservoirs, the physical properties of "early top-late top" type reservoirs are greater than those of "early top-late slope / depression" type reservoirs, which are greater than those of "early slope / depression-late top" type reservoirs.

[0047] The three types of reservoirs are of poor quality.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reservoir quality prediction based on "top- dip- drawdown" stack process analysis, characterized in that, The method comprises the following steps: S1, analyzing the present structural characteristics of the target reservoir according to seismic data; S2, restoring the balanced section to analyze the tectonic evolution process of the reservoir since deposition; S3, analyzing the open and closed evolution process of the reservoir diagenetic system according to the "top-slope-sag" superimposition process of the reservoir; S4, determining the diagenesis and its reservoir-forming effect under different diagenetic systems; S5, reservoir quality classification evaluation and spatial distribution prediction; According to the above steps, the reservoirs are classified into: Class I reservoirs: long-term open system under the conditions of multi-stage uplift exposure and no deep burial; Class II reservoirs: early open-late closed system under the conditions of early uplift exposure and late medium-deep burial; Class III reservoirs: long-term closed system under the conditions of no uplift to the surface and long-term medium-deep burial.

2. The method for reservoir quality prediction based on "top-dip- sag" stack process analysis according to claim 1, characterized in that, The analysis of the present structural characteristics of the target reservoir in S1 comprises analyzing the development characteristics of the unconformity above the reservoir, the overlying strata and the present burial depth; The present structural characteristics are divided into three categories:

1. regional unconformity developed above the reservoir, large amount of overlying strata missing, and present shallow burial; 2. small-scale unconformity developed above the reservoir, part of the overlying strata missing, and present deep burial; 3. no angular unconformity above the reservoir, the overlying strata preserved intact, and present deep burial.

3. The method for reservoir quality prediction based on "top-dip- sag" stack process analysis of claim 1, wherein: In S3, the reservoir is in an open diagenetic system when the strata are uplifted to the surface or near the surface, and the reservoir is in a closed diagenetic system during the burial process of the strata.

4. The method for reservoir quality prediction based on "Top-Dip-Depression" stacking process analysis according to claim 1, characterized in that: In S4, according to the "top-slope-sag" superimposition process, the dissolution is strong and the precipitation is weak in the open diagenetic system, the diagenesis as a whole increases the porosity and permeability, and the reservoir quality is improved better, while the dissolution of the closed diagenetic system forms pores, and at the same time, strong cementation and precipitation occur, and the diagenesis cannot improve the reservoir quality; further, the reservoir quality is predicted through the "top-slope-sag" superimposition of the reservoir during the evolution process.

Images