A method for classifying the causes of seepage barriers in deep-sea channels

Abstract

The present invention relates to a method for classifying the genetic types of seepage barriers in deep-sea waterways, and belongs to the technical field of geological exploration for oil and gas field development. The present invention discloses a method for classifying the genetic types of seepage barriers in deep-sea waterways, comprising obtaining the sedimentation process, scale, lithology, distribution location, and gravity flow genetic type of the deep-sea waterway; classifying the genetic types of the seepage barriers in the deep-sea waterway into landslide-induced seepage barriers, debris flow-induced seepage barriers, low-density turbidite-induced seepage barriers, and semi-pelagic sediment-induced seepage barriers based on the gravity flow genetic type of the deep-sea waterway; and further finely classifying the genetic types of the seepage barriers in combination with the lithology, scale, distribution location, and sedimentation process of the seepage barriers. The present invention fills the gap in the classification scheme of the genetic types of seepage barriers within deep-sea waterways, thereby providing important geological basis and guidance for the evaluation of the continuity and connectivity within the reservoirs of deep-sea waterways.

Description

Technical Field

[0001] The invention relates to a method for classifying genesis types of deep-sea channel seepage barriers, and belongs to the technical field of oil and gas field development and geological exploration. Background Art

[0002] Deepwater channels are the primary transport pathways and depositional sites for deep-sea sediments. As important oil and gas reservoirs in deepwater basins, they are currently a hot topic for deepwater oil and gas exploration and development. However, influenced by factors such as tectonic movement, sea-level fluctuation, provenance, and climatic conditions, deepwater channel sand bodies exhibit complex and variable geometry and a wide variety of rock-phase infill types. Although these reservoirs typically possess good porosity and permeability, their internal structure is complex and variable, with reservoir thickness and connectivity varying significantly even over very short lateral distances. Consequently, turbidite sandstone channel reservoirs often exhibit internal heterogeneity at varying scales. Because seismic resolution is limited in identifying small-scale heterogeneities, characterizing these subsurface reservoirs remains challenging. High permeability differences between reservoir units and non-reservoir layers significantly impact fluid migration during production, severely restricting efficient reservoir development. Previous research has investigated the architectural characteristics of deepwater turbidite sandstone reservoirs, but this research has primarily focused on characterizing sand bodies. The identification and connectivity of seepage barriers between sand bodies within channels has been less explored. Clarifying the types of seepage barriers within deepwater channel reservoirs is crucial for understanding reservoir connectivity. Therefore, a practical method for classifying the genetic types of seepage barriers within deepwater channels is urgently needed. Summary of the Invention

[0003] In order to overcome the defects in the prior art, the present invention aims to provide a method for classifying the types of causes of seepage barriers in deep-sea channels.

[0004] The present invention provides a technical solution to solve the above technical problems: a method for classifying the types of deep-sea channel seepage barriers, comprising the following steps:

[0005] Obtain the sedimentary process, scale, lithology, distribution location and gravity flow genesis type of deep-sea channels;

[0006] Based on the gravity flow genesis of deep-sea channels, the genesis of seepage barriers in deep-sea channels can be divided into seepage barriers caused by landslide, seepage barriers caused by debris flow, seepage barriers caused by low-density turbidite and seepage barriers caused by hemipelagic sedimentation.

[0007] Combined with the lithology, scale, distribution location and sedimentary process of the seepage barrier, the genetic types of the seepage barrier are further divided into fine categories;

[0008] The seepage barrier caused by landslide is finely divided into the seepage barrier caused by landslide gravel mudstone and the seepage barrier caused by landslide siltstone;

[0009] The debris flow-induced seepage barrier is finely divided into bottom-retained mud conglomerate-induced seepage barrier, pebble mudstone-induced seepage barrier, muddy debris flow-induced seepage barrier, and lateral accumulation mud conglomerate-induced seepage barrier.

[0010] The low-density turbidite-induced seepage barrier is finely divided into: layered mudstone-induced seepage barrier, lateral accumulation mudstone-induced seepage barrier, and overlying mudstone-induced seepage barrier.

[0011] The hemipelagic sedimentary seepage barrier is finely divided into hemipelagic drape mudstone seepage barrier.

[0012] A further technical solution is that the seepage barrier caused by the landslide and gravel-containing mudstone is: the lithology is mudstone, gravel-containing mudstone, 3-6m thick, 100-300m wide, distributed at the edge of the waterway, and is formed by the early covering mudstone landslide.

[0013] A further technical solution is that the landslide siltstone-induced seepage barrier is: siltstone, 0.5-3m thick, 10-20m wide, distributed at the edge of the waterway, and formed by the early inner natural levee landslide.

[0014] A further technical solution is that the bottom retained mud conglomerate-induced seepage barrier is: the lithology is mud conglomerate, 1-3m thick, 10-100m wide, distributed at the bottom of the waterway or sandwiched between secondary waterway units, and is mud gravel formed by erosion at the bottom of the waterway.

[0015] A further technical solution is that the pebble mudstone-induced seepage barrier is: the lithology is pebble mudstone, 2-8m thick, 50-470m wide, distributed at the bottom of the waterway, and is an event-induced terrestrial transport deposit.

[0016] A further technical solution is that the seepage barrier caused by the mud debris flow is: the rock type is gravel mudstone and mudstone, 1-10m thick and 50-700m wide, distributed throughout the single waterway, and is eroded and filled by mud-rich debris flow.

[0017] A further technical solution is that the lateral accumulation mud conglomerate-induced seepage barrier is: the rock type is muddy clastic conglomerate, 0.1-2m thick, 5-60m wide, distributed between lateral accumulation secondary waterways, and is formed by mud and gravel eroded at the edge or bottom of the waterway, and then laterally accumulated.

[0018] A further technical solution is that the layered mudstone-derived seepage barrier is composed of mudstone, shale, and siltstone, with a thickness of 0.2-5m and a width of 20-100m, distributed between secondary waterways, and formed in the late stage of gravity flow deposition.

[0019] A further technical solution is that the lateral accumulation mudstone-induced seepage barrier is: the lithology is mudstone, 0.01-0.1m thick, 0.2-1m wide, distributed on the top of the waterway, and formed by lateral accumulation of mudstone.

[0020] A further technical solution is that the mudstone-derived seepage barrier covering the road is: the lithology is mudstone and shale, with a thickness of 0.1-1.5m and a width of >20m, distributed at the bottom and edge of the waterway.

[0021] A further technical solution is that the hemipelagic mudstone-derived seepage barrier is: the lithology is mudstone and shale, the thickness is 1-30m, the width is >200m, and it is distributed on the top of a single waterway.

[0022] The present invention has the following beneficial effects: Based on the genetic type of the filling lithofacies within the channel, it accurately classifies the types of seepage barriers within a single channel, filling the gap in the classification scheme for the genetic type of seepage barriers within deep-water channels. This provides important geological evidence and guidance for evaluating the continuity and connectivity of deep-water channel reservoirs. Therefore, the present invention has important guiding significance for the continuity and connectivity of channel reservoirs in deepwater sediments, as well as for reservoir exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the slump gravel mudstone and slump siltstone of the present invention;

[0024] Figure 2 This is a schematic diagram of an example area of slump gravel-containing mudstone according to the present invention;

[0025] Figure 3 This is a schematic diagram of an example area of slump gravel-containing mudstone according to the present invention;

[0026] Figure 4 Schematic diagram of bottom retained gravel and pebbly mudstone in the present invention;

[0027] Figure 5 This is a schematic diagram of an example area of bottom retained gravel according to the present invention;

[0028] Figure 6 This is a schematic diagram of the pebble mudstone example area of the present invention;

[0029] Figure 7 This is a schematic diagram of the mud debris flow of the present invention;

[0030] Figure 8 This is a schematic diagram of an example area of muddy debris flow according to the present invention;

[0031] Figure 9 This is a schematic diagram of the lateral accumulation mud conglomerate of the present invention;

[0032] Figure 10 This is a schematic diagram of an example area of lateral accumulation mud conglomerate of the present invention;

[0033] Figure 11 This is a schematic diagram of the layered mudstone of the present invention;

[0034] Figure 12 This is a schematic diagram of the layered mudstone example area of the present invention;

[0035] Figure 13 This is a schematic diagram of the lateral accumulation mudstone of the present invention;

[0036] Figure 14 This is a schematic diagram of the lateral accumulation mudstone example area of the present invention;

[0037] Figure 15 This is a schematic diagram of the mudstone covering the road in the present invention;

[0038] Figure 16 This is a schematic diagram of an example area of mudstone covering the road in the present invention;

[0039] Figure 17 This is a schematic diagram of the hemipelagic drape of the present invention;

[0040] Figure 18 This is a schematic diagram of an example area of hemipelagic drape rock according to the present invention;

[0041] Figure 19 This is a similar schematic diagram of the lithology of the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] The present invention provides a method for classifying the genetic types of seepage barriers in deep-sea channels. This method specifically defines and classifies different seepage barriers in waterways based on the morphology, scale, lithology, distribution location, and genesis of seepage barriers within field outcrops. As shown in Table 1, the sedimentary process, scale, lithology, distribution location, and gravity flow genetic type of the deep-sea channel are first obtained. Based on the gravity flow genetic type, the seepage barriers are then classified into four categories: landslide-induced seepage barriers, debris flow-induced seepage barriers, low-density turbidity current-induced seepage barriers, and hemipelagic sediment-induced seepage barriers. Furthermore, the lithology, scale, distribution location, and sedimentary process of the seepage barriers are combined to further refine the genetic type classification of the seepage barriers.

[0044] Table 1

[0045]

[0046]

[0047] There are 4 major categories and 10 subcategories of seepage barriers in deep water channels. The specific classification results are as follows:

[0048] 1) Seepage barrier caused by landslide;

[0049] ① Seepage barrier caused by landslide and gravel-bearing mudstone;

[0050] like Figure 1 、 2 As shown, they are mostly lens-shaped, with the main rock types being mudstone and gravelly mudstone. They are 3-6m thick and 100-300m wide. They are often distributed at the edge of waterways and are mostly formed by early overlying mudstone landslides.

[0051] ② Seepage barrier caused by landslide siltstone;

[0052] like Figure 1 、 3 As shown, they are mostly lens-shaped, with the rock type mainly being siltstone, 0.5-3m thick and 10-20m wide. They are often distributed at the edge of waterways and are mostly inner natural levee collapses formed in the early stage.

[0053] 2) debris flow-induced seepage barriers;

[0054] ① The seepage barrier originated from the bottom retained mud conglomerate;

[0055] like Figure 4 、 5 As shown, they are mostly lens-shaped and layered, and the rock type is mainly mud conglomerate, 1-3m thick and 10-100m wide. They are often distributed at the bottom of the waterway, and a small part is sandwiched between secondary waterway units. Most of them are mud gravel formed by erosion at the bottom of the waterway.

[0056] ② Pebble mudstone-derived seepage barrier;

[0057] like Figure 4 、 6 As shown, these formations are often lens-shaped (flat-topped and convex-bottomed), layered, and primarily comprise pebbly mudstone, 2-8 meters thick and 50-470 meters wide. They are often found at the bottom of waterways and are often deposited by incident terrigenous transport. Pebbly mudstone, like bottom-retained deposits, differs from bottom-retained mud and gravel in that the pebbles in the former are derived from long-distance terrigenous transport, representing distal deposition, while the gravels in the latter are formed by in situ erosion, representing proximal / in situ deposition.

[0058] ③ Seepage barrier caused by muddy debris flow;

[0059] like Figure 7 、 8 As shown, they are mostly lens-shaped, partially layered, and V-shaped. The rock types are mainly gravel mudstone and mudstone. They are 1-10m thick and 50-700m wide. They are often distributed throughout a single waterway and are mostly eroded and filled by mud-rich debris flows.

[0060] ④ Seepage barrier of lateral accumulation mud conglomerate origin;

[0061] like Figure 9 、 10 As shown, they are mostly wedge-shaped or S-shaped, and the rock type is mainly muddy clastic conglomerate, 0.1-2m thick and 5-60m wide. They are often distributed between lateral accumulation secondary waterways, and are mostly formed by mud and gravel eroded at the edge or bottom of the waterway, and then laterally accumulated.

[0062] 3) Seepage barriers caused by low-density turbidite;

[0063] ① Seepage barrier of layered mudstone origin;

[0064] like Figure 11 、 12 As shown, it is mostly layered / banded, with the main rock types being mudstone, shale, and siltstone. It is 0.2-5m thick and 20-100m wide. It is often distributed between secondary waterways and is mostly formed in the late stage of gravity flow deposition.

[0065] ② Seepage barrier of lateral mudstone origin;

[0066] like Figure 13 、 14 As shown, they are mostly wedge-shaped, with the main rock type being mudstone, 0.01-0.1m thick and 0.2-1m wide. They are often distributed at the top of the waterway, gradually tapering from top to bottom, and are often formed by lateral accumulation of mudstone when the sand supply decreases.

[0067] ③ Seepage barrier of mudstone origin covering the road;

[0068] like Figure 15 、 16 As shown, it is mostly wedge-shaped and layered, with the main rock types being mudstone and shale, 0.1-1.5m thick and >20m wide. It is often distributed at the bottom and edge of waterways, and is deposited at the tail of turbidity currents.

[0069] 4) hemipelagic sedimentary seepage barriers;

[0070] ① Seepage barrier of hemipelagic drape mudstone origin;

[0071] like Figure 17 、 18 As shown, it is mostly layered, with the main rock types being mudstone and shale, 1-30m thick and >200m wide. It is mainly distributed at the top of a single waterway and was formed by the sedimentation of semi-pelagic suspended matter during the period of high sea level.

[0072] The above description does not limit the present invention in any form. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can use the technical content disclosed above to make some changes or modifications to equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A method for classifying the causes of seepage barriers in deep-sea channels, characterized in that: The following steps are involved: Obtain the sedimentary process, scale, lithology, distribution location and gravity flow genesis type of deep-sea channels; Based on the gravity flow genesis of deep-sea channels, the genesis of seepage barriers in deep-sea channels can be divided into seepage barriers caused by landslide, seepage barriers caused by debris flow, seepage barriers caused by low-density turbidite and seepage barriers caused by hemipelagic sedimentation. Combined with the lithology, scale, distribution location and sedimentary process of the seepage barrier, the genetic types of the seepage barrier are further divided into fine categories; The seepage barrier caused by landslide is finely divided into the seepage barrier caused by landslide gravel mudstone and the seepage barrier caused by landslide siltstone; The debris flow-induced seepage barrier is finely divided into bottom-retained mud conglomerate-induced seepage barrier, pebble mudstone-induced seepage barrier, muddy debris flow-induced seepage barrier, and lateral accumulation mud conglomerate-induced seepage barrier. The low-density turbidite-induced seepage barrier is finely divided into: layered mudstone-induced seepage barrier, lateral accumulation mudstone-induced seepage barrier, and overlying mudstone-induced seepage barrier. The hemipelagic sedimentary seepage barrier is finely divided into hemipelagic drape mudstone seepage barrier; The seepage barrier caused by the collapse of gravel-bearing mudstone is: the lithology is mudstone and gravel-bearing mudstone, with a thickness of 3-6m and a width of 100-300m, distributed at the edge of the waterway, and is formed by the collapse of the early overlying mudstone; The siltstone-induced seepage barrier is: siltstone, 0.5-3m thick, 10-20m wide, distributed at the edge of the waterway, and formed by the early internal natural levee collapse; The bottom-retained mud-conglomerate-induced seepage barrier is mud-conglomerate with a thickness of 1-3 m and a width of 10-100 m, distributed at the bottom of the waterway or sandwiched between secondary waterway units, and is mud-conglomerate formed by erosion at the bottom of the waterway; The pebble mudstone-induced seepage barrier is: pebble mudstone, 2-8m thick, 50-470m wide, distributed at the bottom of the waterway, and is an event-induced terrigenous transport deposit; The seepage barrier of muddy debris flow origin is: the lithology is gravelly mudstone and mudstone, 1-10m thick and 50-700m wide, distributed throughout the interior of a single waterway, and is eroded and filled by mud-rich debris flow; The lateral accumulation muddy conglomerate-induced seepage barrier is characterized by muddy clastic conglomerate, 0.1-2m thick and 5-60m wide, distributed between lateral accumulation secondary waterways. It is formed by muddy gravel formed by erosion at the edge or bottom of the waterway and then lateral accumulation. The layered mudstone-derived seepage barrier is composed of mudstone, shale, and siltstone, with a thickness of 0.2-5 m and a width of 20-100 m, distributed between secondary waterways, and formed in the late stage of gravity flow deposition; The seepage barrier of lateral accumulation mudstone is: the lithology is mudstone, 0.01-0.1m thick, 0.2-1m wide, distributed at the top of the waterway, formed by lateral accumulation of mudstone; The mudstone-derived seepage barrier covering the passage is composed of mudstone and shale, with a thickness of 0.1-1.5m and a width of more than 20m, distributed at the bottom and edge of the waterway; The hemipelagic mudstone-derived seepage barrier is composed of mudstone and shale, with a thickness of 1-30 m and a width of >200 m, distributed on the top of a single waterway.

Images