CN111766629B - Method for identifying and describing deep carbonate karst structure - Google Patents
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Abstract
The invention discloses a method for identifying and describing a deep carbonate karst structure, which comprises the following steps: identifying a karst development part of a target layer section at a well point of a target area; interpreting an imaging log image, and determining a specific depth range of the development of a karst structure in a target interval; and identifying the characteristics of each composition unit of the karst structure, including the characteristics of a rock core, the characteristics of an imaging logging image and the response characteristics of a conventional logging curve. The method for identifying and describing the deep carbonate karst structure adopts a mode of combining the rock core, the imaging logging image and the natural gamma curve, and can identify the type of the deep carbonate karst structure unit more accurately.
Description
Technical Field
The invention relates to the technical field of carbonate karst detection, in particular to a method for identifying and describing a deep carbonate karst structure.
Background
The fine analysis of the karst structure and the development of the research on the mechanism of the complex karst cause are the focus of the attention of geologists at home and abroad and are one of the hot problems to be solved urgently in the carbonate oil-gas exploration. A large number of scholars develop researches on general characteristics and evolution formation of carbonate karst according to field outcrop data and oil field underground data, and the understanding of the current karst macro structure is not clear. The scientific system is used for describing the karst structure characteristics of the deep carbonate rocks and is an important basis for disclosing the cause mechanism of the deep carbonate rocks.
Imaging logging is a logging technology which is popular in recent years, overcomes the defects of low seismic profile resolution, low deep core heart rate and low conventional logging accuracy, and becomes the most intuitive and accurate data reflecting underground stratum information. Through the imaging logging technology, a large amount of visual image information can be provided for analyzing the sedimentary structural characteristics of the stratum, and cracks, karst caves, karst holes and the like formed in the carbonate stratum can be extracted for semi-quantitative analysis. Although the application of imaging logging is continuously popularized, the method for comprehensively and finely depicting deep carbonate karst structural units by taking imaging logging information as a main part and other information as an auxiliary part is still very deficient.
And (4) establishing a deep karst structure model through the observation of modern karst or ancient karst outcrop.
The karst reservoir stratum is an important target for oil-gas exploration of Ordovician carbonate rocks all over the world. Unlike modern karsts, deep ancient karsts have the characteristics of large burial depth and complex structure. The fine analysis of the karst structure and the development of the research on the mechanism of the complex karst cause are the focus of the attention of geologists at home and abroad and are one of the hot problems to be solved urgently in the carbonate oil-gas exploration.
In the last two thirty years, based on modern karst process and field outcrop analysis, a large number of scholars conduct extensive research on karst structure and control factors, and establish various evolution modes to explain the formation process of deep carbonate karst. Based on modern karst and field outcrop, important knowledge is obtained in the aspect of research of a karst cave structure, and the karst cave is divided into a funnel type, a tubular branch type, a plate-shaped bedding distribution type, a karst cave group and other various form types in the aspect of form scale of the karst cave; in the aspect of filling karst caves, 3 types of filling materials such as crack cobbles, mixed cobbles, cave deposition filling and the like are divided; in the aspect of karst cave and associated construction, the important roles of the gravel formed by karst cave collapse and associated fault and crack in the karst structure are emphasized. The comprehensive pore network system formed by karst caves of different levels and erosion pores, cracks, cave collapse gravels and the like related to the karst caves is an important oil and gas storage space.
Deep karst structures are depicted by earthquakes, conventional well logging and cores.
With the continuous abundance of downhole data, deep karst systems can be identified by seismic and conventional well logging. Karst reservoirs have a characteristic response on seismic reflections that is beaded or horizontally strong. Through the interpretation of the well-passing sections of different karst landform units, the reflection characteristics can be found to have a certain distribution rule on the ancient landform units. The beaded reflection mostly appears in a karst highland and a karst steep slope area with higher denudation degree, and the slope area is mainly abnormal in parallel strong reflection. Karst action in karst depression areas is extremely weak and no special seismic reflection characteristics exist. The differences in seismic reflection characteristics reflect, to some extent, the internal differences in karst structure. Generally speaking, the cavern with the hole height of 0.5-5 m has no obvious abnormality on earthquake and well drilling, and the cavern with the hole height of more than 5m can be displayed on three-dimensional seismic data. Due to the limitation of seismic resolution, the longitudinally drilled solution cavity cannot show the complete external form on the seismic section.
The accuracy of seismic data is limited, and only the seismic reflection abnormity of the whole karst zone can be described, and the data with higher accuracy, such as rock cores, well logging and the like, is needed for accurately describing the characteristics of the interior of the karst zone. However, the drilling and coring costs of deep carbonate rock are high, the possibility of coring in the whole well section is low from the production point of view, particularly, the pressure is released when the drill meets a karst cave, the difficulty of drilling and coring is high, and even if cores in different well sections exist, the cores are influenced by the coring rate and the homing accuracy, and the core is not representative for reflecting the overall characteristics of the stratum.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the existing defects and provide a method for identifying and describing the deep carbonate karst structure, wherein the types of deep carbonate karst structure units can be more accurately identified by combining a rock core, an imaging logging image and a natural gamma curve, and the problems in the background technology can be effectively solved.
In order to solve the technical problems, the invention provides the following technical scheme:
the invention provides a method for identifying a deep carbonate karst structure, which comprises the following steps:
s1: identifying a karst development part of a target layer section at a well point of a target area;
s2: interpreting an imaging log image, and determining a specific depth range of the development of a karst structure in a target interval;
s3: and identifying the characteristics of each composition unit of the karst structure, including the characteristics of a rock core, the characteristics of an imaging logging image and the response characteristics of a conventional logging curve.
As a preferable scheme, the step S1 includes:
firstly, selecting a seismic section of a well point in a target area, carrying out well seismic comparison, carrying out horizon calibration on a target interval, determining the position of the target interval on the seismic section, identifying the characteristics of seismic reflection event of the target interval on the event, and indicating the development of a karst cave if a longitudinal bead-shaped reflection or a transverse enhanced amplitude reflection band appears.
As a preferable scheme, the step S2 includes:
according to the target interval position calibrated by the well earthquake in the step S1, carrying out karst structure recognition at the corresponding position on the imaging logging image, firstly carrying out imaging logging image interpretation of the coring section on the single well target interval with coring, calibrating the rock structure and the structural characteristics on the rock core with the same depth with the imaging logging image, obtaining the accurate depth of the target structural characteristics, and obtaining the expression patterns of various karst structures in the imaging logging image.
As a preferable scheme, the step S3 includes:
and (3) identifying each karst structural unit by comprehensive imaging logging and conventional logging curves, particularly natural gamma curve characteristics.
As a preferred scheme, the identification method is as follows:
1) identifying filling characteristics in the karst cave according to the form and color characteristics of an imaging logging image of the karst cave development layer section and by combining a natural gamma value, wherein the filling characteristics comprise the stacking characteristics of filling materials, the arrangement mode of filling breccia and the relative mud content in the filling materials;
2) after image recognition is carried out on different karst structural units, further fine division can be carried out according to the difference of gamma ray, neutron porosity, sound wave, lithology density logging and resistivity conventional logging values;
3) For well points without imaging logging images, karst cave and non-karst cave strata can be identified through statistical analysis of conventional logging values, five sensitive parameters of lithologic density logging, neutron porosity, mudstone content logging, absolute values of differences of shallow lateral conductivity and bilateral conductivity are selected to carry out pairwise intersection, and a karst cave layer and a non-karst cave layer can be determined according to a distribution range of the logging values on an intersection map.
A method of describing a deep carbonate karst structure, the method of describing comprising the steps of:
s1: dividing the single-well karst structure, namely dividing the longitudinal composition of the single-well karst structure according to the type of each karst structure unit determined by the scheme and the imaging logging image characteristics corresponding to the karst structure units;
s2: a step of comparing well-connecting karst profiles, which is to select well-connecting profiles in multiple directions in a research area on the basis of dividing each single-well karst structure, compare the karst structure units among wells and divide the karst evolution period;
s3: 2, selecting a typical single well by taking the imaging logging image characteristics of each karst unit in the step 2 as reference, explaining the imaging logging of the karst development section on the single well, and analyzing the combination form, distribution type and characteristics of the karst structural units in the longitudinal direction;
S4: and after vertically analyzing the karst characteristics of the typical single well, selecting a plurality of transverse and longitudinal well connecting sections in a target area, carrying out transverse comparison, and analyzing the evolution period of the karst structure by combining the regional evolution characteristics of the target area.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
(1) in the process of identifying the karst structural units, the method can more accurately identify the types of the deep carbonate karst structural units by combining the rock core, the imaging logging image and the natural gamma curve.
(2) In the identification structure of the karst structural unit, imaging logging images are largely adopted to finely depict the karst structural unit without the core well, so that the identification precision of the karst structural unit is improved.
(3) In the process of dividing the single-well karst structural units, the method for identifying the karst structural units improves the accuracy of identifying the single-well longitudinal karst structural units and the combination thereof.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
In the drawings:
fig. 1 is a schematic flow chart of a method for identifying a deep carbonate karst structure in an embodiment of the invention.
Fig. 1A is a core calibration diagram of an imaging log image in the method for identifying a deep carbonate karst structure in the embodiment of the present invention.
Fig. 1B is a core calibration diagram of another imaging log image in the method for identifying a deep carbonate karst structure in the embodiment of the present invention.
Fig. 2A is a schematic diagram of a static image of a formation subjected to erosion in the method for identifying a deep carbonate karst structure in the embodiment of the present invention.
Fig. 2B is a schematic illustration of a static image of another eroded formation in the method for identifying a deep carbonate karst structure according to the embodiment of the present invention.
Fig. 3A, fig. 3B, fig. 3C, fig. 4A, fig. 4B, fig. 4C, fig. 5A, fig. 5B, fig. 6A, fig. 6B, fig. 7A, fig. 7B, fig. 7C, and fig. 8 are schematic structural feature diagrams of finely identifying each constituent unit of the karst system by combining a dynamic image and a static image in the method for identifying the deep carbonate karst structure according to the embodiment of the present invention.
Fig. 9, fig. 10, fig. 11 and fig. 12 are schematic diagrams of longitudinal combinations of various modes of images in the method for identifying the deep carbonate karst structure in the embodiment of the invention.
Fig. 13 is a schematic diagram of a total thickness of a stratum in the eagle mountain group in drilling meeting on a west ancient karst slope of a north slope in a tower in an identification method of a deep carbonate karst structure in an embodiment of the invention being 168 m.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
For better understanding of the above technical solutions, the following detailed descriptions will be provided in conjunction with the drawings and the detailed description of the present invention.
The embodiment is as follows:
referring to fig. 1, the present embodiment provides a method for identifying a deep carbonate karst structure, including the following steps:
s1: identifying karst development interval by seismic profiling
Generally speaking, the cavern with the hole height of 0.5-5 m has no obvious abnormality on earthquake and well drilling, and the cavern with the hole height of more than 5m can be displayed on three-dimensional seismic data. The typical seismic section of a research area is explained by using Landmark software, and due to the limitation of seismic resolution, the karst caves encountered by longitudinal drilling cannot display the finished external form on the seismic section, but are the characteristic response of typical bead-shaped or horizontal strong reflection, which is also the main seismic identification characteristic of large-scale epigenetic karst caves, and the specific depth of a karst development section is obtained by mutually calibrating a logging curve and the seismic section;
S2: obtaining an imaging log image of a target interval
The imaging logging instrument is used for obtaining a digital matrix of resistivity through simultaneous recording of a plurality of electrodes, and after a series of digital and image processing such as data recovery, image generation, image enhancement and the like, the digital matrix is converted into a two-dimensional image which reflects the relative size of the resistivity of the borehole wall and the formation and is represented by a color scale, wherein the two-dimensional image comprises a static image and a dynamic image, the color of the color scale is black-brown-yellow-white and represents the change of the resistivity from low to high, and the static image is formed by adopting the same color scale in the whole measuring well section and is usually used for reflecting the whole change of lithology; the dynamic image is normalized in a small range, so that the detail change of the stratum in the small range is highlighted, the imaging logging image is generally displayed as a planar expansion diagram, namely, the imaging logging image is expanded along a shaft from the true north direction, and the imaging logging image is projected on the planar diagram according to the azimuth sequence of left to right, north (0 degrees), east (90 degrees), south (180 degrees), west (270 degrees) and north (360 degrees). And intercepting the karst development layer section to perform fine imaging well logging interpretation according to the result of the first step of well seismic calibration. In the interpretation process of the imaging logging, a natural gamma curve is combined, because the natural gamma logging is sensitive to the response of the argillaceous substances, the abnormal high value of the natural gamma is usually displayed under the condition that the karst development layer is filled with the argillaceous substances, the characteristics of the filling substances in the karst system can be accurately judged by matching with the natural gamma curve, and then the formation mechanism of the karst system is explained,
S3: calibrating an imaging log image using a core
The resolution scale of the imaged log image is substantially consistent with the core. Therefore, in order to ensure the reasonability and the accuracy of the imaging logging interpretation, the corresponding imaging logging images are mutually calibrated by using limited coring data, and the imaging logging is used for guiding the core to be classified into the core and simultaneously depicting the type of the imaging logging image so as to more accurately interpret the imaging logging image without coring;
for example, FIG. 1A shows a light gray brilliant-grained tuff in the surrounding rock, a small cavern filled with cobbles in the upper part, a clear washout surface characteristic at the bottom of the cavern, level bedding of the filled cobbles and the dark mudstone, and directional arrangement of the cobbles. The corresponding imaging logging image shows that the characteristics of the upper and lower images of the contact surface have mutability, the upper part is filled with light and dark strips with bedding characteristics, and the lower part of the surrounding rock is in a high-resistance block shape. The natural gamma curve shows an increasing trend on the karst cave filling layer and is a response to the increase of the mud content of the filling material.
In the figure 1B, when a small karst cave is drilled on a core at the position of 5560m, substances in the cave are crushed, and filled calcite breccia can be seen, and the resistivity of the limestone with light gray bright crystal and crumbled sand is obviously different from that of surrounding rocks. The karst cave part is seen to be dark brown block-shaped response on the imaging logging static image, and the filling material in the cave can be seen to have low-resistance dark substances and high-resistance bright white pebble-shaped substances on the dynamic image, which is just calcite pebble. The bottom of the visible hole in the core has a dark mud filled crack corresponding to a dark band on a bright yellow background on the imaged log image. Meanwhile, the response of the natural gamma ray logging curve to the karst cave and the surrounding rocks also has a suddenly reduced variation trend.
S4: imaging logging image identification template for establishing karst structural unit
Processing the electrical imaging logging data to obtain image information of the logging data, wherein the image information comprises a dynamic image and a static image, the image information comprises the structure and the color of the image, and the static image is used for uniformly performing normalization processing on the whole measuring well section and can provide absolute reference for lithology interpretation; the dynamic image is normalized by applying an image dynamic enhancement algorithm in a small range, and aims to highlight the fine features of the stratum.
The static image of the formation where erosion occurred is brown-dark brown, which has a distinct boundary in image color from the formation where erosion did not occur. An unconsolidated formation typically has the following 2 image characteristics:
firstly, both static images and dynamic images are bright yellow blocks (figure 2A), the whole thickness is large, dark bands are few in the interior, high-resistance bright-color block images are often argillaceous limestone, algae bonded limestone and the like which are stably deposited in a low-energy environment, the lithology is compact, the thickness is large, the corrosion resistance is poor, and the high-resistance bright-color block images are generally used as watertight interlayers in a karst system.
And (3) a bright high-resistance horizontal stripe image (fig. 2B), wherein the whole color of the static image is bright yellow-orange, and the dark and light stripes are alternated. The thickness of the strip is about 0.1m, no special drilling response exists, the natural gamma is extremely low, the energy of the sedimentary water body changes in a gyric manner, the sedimentary lithology changes, the resistivity changes, the overall resistivity is relatively low, and the strip serves as a watertight interlayer in a karst system.
And (5) interpreting the imaging logging image, and identifying the deep carbonate karst structural unit according to the image characteristics. After a karst system is identified on a static image, the structural characteristics of each component unit of the karst system are finely identified by combining the dynamic image and the static image, and the total number of the images is 11;
firstly, a static image is a dark brown-black block (figure 3A), the color distribution is uniform, no obvious bedding characteristic exists, the thickness is generally 1-10m, a dynamic image can see slight change and occasionally small bright color patches, and the dark block phase is a mud filled karst cave response;
secondly, the whole color of the static image is darker (fig. 3B), generally light brown-brown, dark bands distributed in parallel can be seen, the thickness of the bands is about 0.1m or more, and the dark bands can be seen from the dynamic image and can be thin layers of cellular karst pore development or small karst cavities filled with mud;
thirdly, strips with alternate light and dark are distributed vertically (figure 3C), different from horizontal strips, the vertical strips are special forms of collapse and slippage of stratum in the drilling process, generally along with drilling fluid loss and increase in drilling time, the whole body has the logging response characteristics of low resistance and high gamma, and the drilling response characteristics are also likely to be the result of sudden change of drilling speed when the drilling meets karst caves;
A light and dark thin interbed (figure 4A) under the background of integral dark low resistance has higher density of layers which are all below 0.1m, the image type is often positioned on the upper part of dark massive images which are close to the unconformity surface of the stratum and are response of ancient soil or mud fillers on the top of a large karst cave near the unconformity surface;
randomly distributed bright plaques (figure 4B) under a bright background, wherein the plaques are different in size, fuzzy in boundary, and non-sequential in arrangement, are karst gravels which are locally crushed, are filled by low-resistance mud among the gravels, and are formed by compacting and closely contacting the gravels in the later compacting process;
sixthly, the image is a disorder distribution bright color patch under a dark background (figure 4C), the overall resistivity is low, particularly, the disorder distribution of high resistance patches with different sizes can be seen in a dynamic image, surrounding rock and gravel are filled in the karst cave, the mud content among the gravel is high, and the gravel can be partially carried in the underground fluid movement process;
seventhly, bright and color ordered plaque images (figure 5A) under dark background, wherein bright and color plaques are arranged in order, the boundaries of the plaques are clear and uniform in size, karst gravels are not conveyed and are cracked and deposited in situ, the gravels are in line contact with each other, dark color filling is carried out among the gravels, and cracks are developed at the top of the karst cave but are not collapsed;
The bright background is pinhole-shaped or honeycomb-shaped small dark spots (figure 5B), the spots are various in shape and are distributed disorderly and randomly, and are small corrosion holes, such corrosion holes are mostly associated with solution expansion cracks, sometimes, the layered spots are pinhole-shaped spots meter-level layered distribution, the thickness is about 1m, the layered distribution is a pore dissolving layer, and the layers are mostly separated by a bright interlayer;
ninthly, a plurality of dark sine curves are distributed nearly in parallel on the bright yellow background (figure 6A), the sine curves are high-angle cracks, the thickness of the curves is uneven, and the thickened parts are often subjected to diffusion and dissolution phenomena in different degrees along the crack surfaces;
a bright red staggered mesh image (fig. 6B), which is relatively bright in overall color, and has different amplitudes of sinusoids distributed in a staggered manner, and is characterized in that multi-stage structural cracks develop, the cracks are in an open or argillaceous filling state, the image is generally the main response characteristic of a seepage zone in a karst system, the cracks can be further divided into high-angle cracks, low-angle cracks and mesh cracks according to the occurrence (fig. 7), the low-angle cracks are expressed as flat dark sinusoids on an imaging logging image, the high-angle cracks are expressed as high-steep sinusoids on the imaging logging image, the mesh cracks are generally intersected by more than two groups of sinusoids, and a mesh structure is expressed on the imaging logging image (fig. 6A, fig. 6B, fig. 7A, fig. 7B, fig. 7C and fig. 8);
The dark unidirectional network image (fig. 8) has dark background color, generally brown-dark brown, and nearly vertical black stripes are distributed nearly in parallel, and it is considered that vertical cracks are densely distributed, often accompanied by disorderly distributed erosion holes, and the overall resistivity is very low, which is the most favorable type of the developmental phase of the reservoir.
S5: method for establishing longitudinal development mode of karst structure through combination form of imaging logging image units
The karst cave is a main structure of a karst system, and the karst cave, associated fracture stratums at the upper part and the lower part of the karst cave and fillers inside the karst cave jointly form a longitudinal structure of the karst system and are generally displayed as longitudinal combinations of different modes of multiple images on an imaging logging image.
Referring to fig. 9, the static image is dark block-shaped, and has a distinct boundary with the image colors of the upper and lower strata, the filling material at the bottom of the cave is in abrupt contact with the original bottom layer, the imaged logging image changes from dark brown to bright yellow, and can be judged to be a karst cave with a longitudinal depth of about 12m, and then the filling characteristics of the karst cave can be analyzed through the dynamic image, the two ends with the deepest color are dark block-shaped images, which are two mud filled karst caves, and the lower dark block-shaped image has floating bright color patches, which are carbonate rock pebbles filled in the karst cave.
Referring to fig. 10, a karst cave is filled in two sections mainly containing cobbles, the longitudinal depth can reach 25m, and a dark layered image at 5100m larger scale is a response characteristic of low-resistance ancient soil near the unconformity surface of the cave top. It is about 12m down, and the imaging log image is dark block-shaped. 5101-5116 m is an upper cave, 5101-5107 m of the top corresponds to a dark massive phase and is a cave section filled with high-content mud, although broken gravel can be seen from a dynamic image, the boundary of the gravel is fuzzy and has different sizes, and the broken gravel can be seen through multi-period scouring and erosion even the erosion of mud and sand filling materials to the gravel is seen, so that the composition of the gravel is complex, meanwhile, the content of retained mud is sharply increased, and the response characteristics of extremely low resistance and extremely high natural gamma value are caused. 5107-5112 m is reduced relative to the natural gamma value of the upper part, broken surrounding rock breccia can be distinguished on a static image, the broken surrounding rock breccia is distributed in a floating manner in the muddy filling, the muddy content is reduced compared with the upper part, but the filling still mainly contains the muddy. 5113-5115 m is used for filling and piling up the 3m thick corner gravel, mainly high-resistance ordered patch images under a low-resistance background are used, the boundaries of the corner gravel can be clearly distinguished no matter whether static images or dynamic images are used, the corner gravel forms a contact relation of surface contact, cracks filled with mud are formed among the corner gravel, the content of mud filling materials among the cracks is extremely low according to a flat low-value natural gamma curve, and it can be seen that no obvious displacement occurs in broken corner gravel at the bottom of a cave. 5116-5122 m is a cave of another stage, the top of the cave is a low-resistance unidirectional network image, a group of near-vertical cracks communicate the cave with the previous cave to serve as a passage of underground fluid, the cave of the stage is mainly filled with mud, a small amount of floating high-resistance bright-colored cobbles are filled in the filling, and the filling is recovered to an original surrounding rock stratum from 5122 m.
Referring to fig. 11, the longitudinal depth of the cave is about 10m, and according to the imaging log image, the imaging log phase of 6126-6127 m is a dark low-resistance block image, which is filled with mud at the top of the cave, and only a small amount of floating high-resistance gravel is present. 6128-6132 m is the subject part of the karst cave and is a karst gravel section, the karst erosion degree is high, cracks among the karts are filled with mud, the natural gamma value is higher and is about 70API, 6131-6132 m is a section of low-resistance block images, the mud content is increased, and a small peak value of a natural gamma curve is formed. The karst cave is small in scale on the whole and poor in filling material sequence, and the mud content is gradually reduced due to the fact that the cave top faces downwards, and the formed natural gamma rays are characterized by the tendency of being changed from high to low on the whole. The gravel filling with cracks is characterized in that the gravel is relatively single in composition and is not sorted, mud and calcite fill the gaps between the gravel, and the mud is filled downwards through cracks between the gravel and is deposited to the bottommost part of the cave.
Referring to fig. 12, the longitudinal depth of the cavern is about 12m, the main body of the cavern is 5263-5273 m, and a set of high-angle cracks develops on the undisturbed bottom layer of the cavern top, which may be the result of cave collapse and gravity unloading. The cave filling material can be divided into three sections from top to bottom, which are respectively:
(1) Visible light and shade alternate layered images are displayed on the imaging logging image, the top layer of the imaging logging image is filled with the silt, and the imaging logging image is layered horizontally;
(2) bright color patch-shaped images (5268-5271 m) are floating-shaped gravel filling sections, the stacking mode of the gravel gradually becomes loose from bottom to top, the mud content is increased, and the gravel is changed into a floating shape from the surface contact mode at the lower part to the top;
(3) dark block image, hole bottom mud filling section, mud filling with deposition thickness of about 2m
Because the ancient karst exposed in the field and the ancient karst developed in the deep stratum have difference of causative mechanism, the structural characteristics of the deep karst cannot be directly deduced according to the observation result of the field outcrop; the main data of deep strata such as earthquake, rock core and the like have certain limitation on the aspect of analyzing the karst structure, so that a large number of high-precision imaging logging images become important data for analyzing the deep carbonate karst structure. The position of the karst system can be accurately positioned through earthquake and core calibration, and then the identification template of the karst structure unit in the research area is established through fine interpretation of imaging logging.
Referring to fig. 13, the middle ancient 111 well is located on the west karst slope of the north slope in the tower, and the total thickness of the stratum of the eagle mountain drilling group is 168 m.
Dividing the longitudinal structure of the single-well karst structure according to the single-well karst structure division, the types of the karst structure units determined by the scheme and the imaging logging image characteristics corresponding to the karst structure units;
and a step of comparing well-connected karst sections, namely selecting well-connected sections in multiple directions in a research area on the basis of the division of each single-well karst structure, comparing the karst structural units among the wells, dividing the karst evolution period, combining well and earthquake, and determining that the karst development section of a target layer section is 6080-6180 m and the seismic section has typical string bead reflection characteristics.
According to the division of karst structural units, wherein 6080-6093 m is a surface karst section, the natural gamma value of the top interface of the eagle-mountain group is suddenly increased, and an imaging logging image is a light and dark alternate thin layer, belongs to a large karst cave on the surface layer and is filled with mud. 6093-6182 m is a crack solution hole development intensive section, and a cave with the height of about 4m is filled by mud is arranged at the 6093m position. The imaging logging image shows disordered dark speck-shaped dissolving holes and dark reticular structure dissolving seams, and cracks and dissolving holes are more densely developed at the position close to the surface karst zone. At 6102.5m and 6104m near the surface zone of the karst there is a cavern development filled with mud of a height of about 0.5 m. 6182m to the bottom of the well, the imaging log is displayed as a bright yellow block or strip, and the gamma curve is relatively straight and is a high-barrier layer section.
And dividing the combination characteristics of the single-well karst structural units in the longitudinal direction. The surface layer argillaceous filling karst caves are filled from top to bottom, namely the low-angle cracks and the small karst caves are filled, and the high-angle cracks and the karst cave dense sections are filled.
And carrying out comparison on the karst structure of the connected wells. The karst cave layers are transversely compared, and 3 sets of transversely contrastive karst cave layers can be identified in the target layer section. Wherein the karst cave layer which is 40-100m away from the top surface of the eagle mountain group is widely distributed. The formation mechanism of the karst structure is further discussed on the basis of the contrast profile of the karst structure.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (2)
1. A method for identifying a deep carbonate karst structure is characterized by comprising the following steps: the method comprises the following steps:
s1: identifying a karst development part of a target interval at a target area well point, selecting a seismic section of the target area well point, comparing well seismic, calibrating the layer position of the target interval, determining the position of the target interval on the seismic section, identifying the characteristics of seismic reflection event of the target interval, and indicating the development of a karst cave if a longitudinal bead-shaped reflection or a transverse enhanced amplitude reflection band appears;
S2: interpreting imaging logging images, and determining a specific depth range of development of a karst structure in a target interval: according to the target interval position calibrated by the well earthquake in the step S1, carrying out karst structure recognition at the corresponding position on the imaging logging image, firstly, carrying out imaging logging image interpretation of the coring section on the single well target interval with coring, and calibrating the rock structure and the structural characteristics on the rock core with the same depth with the imaging logging image to obtain the accurate depth of the target structural characteristics and the expression patterns of various karst structures in the imaging logging image;
s3: identifying the characteristics of each component unit of the karst structure, including the characteristics of a rock core, the characteristics of an imaging logging image and the response characteristics of a conventional logging curve, wherein the identification process comprises the following steps:
1) identifying filling characteristics in the karst cave according to the form and color characteristics of an imaging logging image of the karst cave development layer section and by combining a natural gamma value, wherein the filling characteristics comprise the stacking characteristics of filling materials, the arrangement mode of filling breccia and the relative mud content in the filling materials;
2) for well points without imaging logging images, identifying karst cave and non-karst cave stratums by statistical analysis of conventional logging values, selecting five sensitive parameters of lithologic density logging, neutron porosity, mudstone content logging, absolute values of differences between shallow lateral conductivity and bilateral conductivity to carry out pairwise intersection, and determining a karst cave layer and a non-karst cave layer according to a distribution range of the logging values on an intersection map;
S4: establishing an imaging logging image identification template of a karst structure unit, processing electrical imaging logging data to obtain image information of the logging data, wherein the image information comprises a dynamic image and a static image, the image information comprises the structure and the color of the image, and the static image is used for uniformly performing normalization processing on the whole measuring well section and can provide absolute reference for lithology interpretation; the dynamic image is normalized by applying an image dynamic enhancement algorithm in a small range, and aims to highlight the fine features of the stratum, interpret the imaging logging image and identify the deep carbonate karst structural unit according to the image features.
2. A method for describing a deep carbonate karst structure identified by the method for identifying a deep carbonate karst structure of claim 1, characterized by: the description method comprises the following steps:
s1: dividing the single-well karst structure, namely dividing the longitudinal composition of the single-well karst structure according to the determined type of each karst structure unit and the imaging logging image characteristics corresponding to the karst structure unit;
s2: a step of comparing well-connecting karst profiles, which is to select well-connecting profiles in multiple directions in a research area on the basis of dividing each single-well karst structure, compare the karst structure units among wells and divide the karst evolution period;
S3: selecting a typical single well by taking the imaging logging image characteristics of each karst unit in the step 2 as a reference, explaining the imaging logging of a karst development section on the single well, and analyzing the combination form, the distribution type and the characteristics of the karst structural units in the longitudinal direction;
s4: and after vertically analyzing the karst characteristics of the typical single well, selecting a plurality of transverse and longitudinal well connecting sections in a target area, carrying out transverse comparison, and analyzing the evolution period of the karst structure by combining the regional evolution characteristics of the target area.
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| CN114086948B (en) * | 2020-12-08 | 2023-11-28 | 中国石油天然气集团有限公司 | Carbonate rock classification and identification method and device, computer equipment and storage medium |
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| CN113916192B (en) * | 2021-11-05 | 2023-06-23 | 郑州信息科技职业学院 | Karst cave image acquisition monitoring and imaging system |
| CN114386154B (en) * | 2022-01-14 | 2023-12-15 | 中水珠江规划勘测设计有限公司 | Method and device for determining influence depth of dam foundation modern karst layer and electronic equipment |
| CN114998367B (en) * | 2022-06-06 | 2024-03-22 | 浙江数智交院科技股份有限公司 | Planar partitioning method and device for karst development degree and electronic equipment |
| CN115506776A (en) * | 2022-09-23 | 2022-12-23 | 成都理工大学 | Method for identifying soluble texture of carbonate reservoir |
| CN116184527B (en) * | 2023-04-25 | 2023-07-11 | 西南石油大学 | Magma rock lithology discrimination method and device based on element logging and imaging logging |
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