Fracture-cavity Reservoirs Research Articles

Construction of carbonate reservoir knowledge base and its application in fracture-cavity reservoir geological modeling

To improve the efficiency and accuracy of carbonate reservoir research, a unified reservoir knowledge base linking geological knowledge management with reservoir research is proposed. The reservoir knowledge base serves high-quality analysis, evaluation, description and geological modeling of reservoirs. The knowledge framework is divided into three categories: technical service standard, technical research method and professional knowledge and cases related to geological objects. In order to build a knowledge base, first of all, it is necessary to form a knowledge classification system and knowledge description standards; secondly, to sort out theoretical understandings and various technical methods for different geologic objects and work out a technical service standard package according to the technical standard; thirdly, to collect typical outcrop and reservoir cases, constantly expand the content of the knowledge base through systematic extraction, sorting and saving, and construct professional knowledge about geological objects. Through the use of encyclopedia based collaborative editing architecture, knowledge construction and sharing can be realized. Geological objects and related attribute parameters can be automatically extracted by using natural language processing (NLP) technology, and outcrop data can be collected by using modern fine measurement technology, to enhance the efficiency of knowledge acquisition, extraction and sorting. In this paper, the geological modeling of fracture-cavity reservoir in the Tarim Basin is taken as an example to illustrate the construction of knowledge base of carbonate reservoir and its application in geological modeling of fracture-cavity carbonate reservoir.

Formation of hoodoo-upland on Ordovician karst slope and its significance in petroleum geology in Tahe area, Tarim Basin, NW China

Based on a large number of geological and geophysical data, the formation, fracture-caves types and hydrocarbon distribution of hoodoo-upland on the Ordovician karst slope in the Tahe area, Tarim Basin, are discussed by analyzing faults and strata thickness. The hoodoo-upland was made of high peaks and narrow valleys in the Ordovician karst slope during the Early Hercynian karst period, which were distributed along the NNE positive flower structure and had inherited evolution. The fault-fractures and fracture-vugs complex were extremely developed, with a thickness of 100 m. The cumulative oil production of 60% oil wells was more than 20×104 t per well in the hoodoo-upland, where the residual thickness of the Ordovician Yingshan Formation was greater than karst depressions. Caves formed by the shelter of collapsed breccias were developed in the valleys. They were 1.6 to 13.5 m high, with a filling rate of 51.6%. The positive flower structure under the settings of strike-slip compression controlled the early formation of the hoodoo-upland on the karst slope, resulting in the differences of drainage distribution and karstification. Compared with the water-rich karst valley, the hoodoo-upland with lean water suffered weaker karstification, had thicker residual stratum, and was higher in terrain. In rainy season, the meteoric water flew and corrode along the cracks, forming a complex network of fractures and caves. Combined with inherited uplift and the effective match of the NNE deep faults, oil and gas continuously charged into the reservoir space in the upland, forming the hoodoo fracture-cave reservoir with vertically quasi continuous distribution, high hydrocarbon abundance and high production.

Study on the coupling calculation model of dump flooding in Hala-hatang fracture-cavity reservoir

Abstract The dump flooding technology comes from offshore oil fields. It is necessary to increase the production of oil by water injection when fracture-cavity reservoirs in Xinjiang enter their middle and later stages. Lack of water sources in the desert area and the presence of heavy upper water layers encourage further research into the application of this technology. The dump flooding technology can eliminate the need for specialized injection wells and reduce the consumption of oil fields in the surface water sources, which may significantly aid in the development of the local economy and environment. In China, the research on dump flooding is still in its preliminary phase. Hence, there is no complete flow model for gravity flow and no optimization design software to optimize the development effect. This article sets up a flow model of a water layer-well-fracture unit by key local nodes. The key nodes, such as some perforating water layer, the bullet hole or the water valve, were simulated using the COMSOL software. The flow equations of each node were coupled together for the system-wide flow coupling model to verify the whole system by the numerical simulation, which needs Eclipse to run. The results of the research can be used to predict the water injection rates and formation pressures, and also provide a reference and a basis for the optimal design of water injection.

Research on fluid flow mechanism of fracture-cave carbonate reservoirs based on fluid mechanics

ABSTRACT Facture-cave carbonate reservoir has not formed mature development theory and method up to now, and the development is world-class difficult problems, which are caused by that it is not clear to understand the particularity of reservoir characteristics and fluid flow mechanism. Because karst caves are the dominant reservoir space and production contributor, porous flow mechanics is not applicable. Reservoir body belongs to neither porous media nor continuum as a whole, hence fluid flow belongs to the research category of fluid mechanics. Contrary to widely adopted coupling method, this paper will focus on the fluid flow mechanism by only applying the theory of fluid mechanics and ignoring porous flow on the basis of analyzing the particularity of reservoir characteristics. Both capillary pores in carbonate matrix and slender dissolved cavities can be regarded as hydraulic long pipe, and fluid flow conforms to pipe flow law. Fluid flow in fracture belongs to parallel plate clearance differential pressure flow, which is similar to pipe flow. Fluid is static under gravity and fluid flow conforms to hydrostatics law in approximately equiaxed karst caves, and fluid flow out of karst cave is orifice outflow. Porous flow in reservoirs is unified with pipe flow. The essence of porous flow is the macro performance of pipe flow in countless capillary pores, which manifests as Darcy’s law under laminar condition. Porous flow in carbonate matrix can be completely ignored because it is extremely difficult to occur and the effect is very tiny. In dissolved-cavity reservoir body of millimeter scale, fluid flow is mainly slight pipe flow and gravity effect is significant, which leads to tiny production pressure differential and pressure drop funnel. In karst-cave reservoir body of meter scale, there is no fluid flow nor pressure drop in horizontal direction and the displacement of oil by water is piston-like displacement vertically upward in karst caves, hence pressure drop funnel does not exist at all. The production pressure differential generated by orifice outflow at the outlet of karst cave is very tiny and can be ignored. The new fluid flow mechanism based on fluid mechanics will provide theoretical basis for solving the difficult problems of developing fracture-cave carbonate reservoirs.

Mechanism of Connecting Natural Caves and Wells Through Hydraulic Fracturing in Fracture-Cavity Reservoirs

In karst fracture-cavity reservoirs, the oil/gas is primarily distributed in natural fractures and caves. Therefore, hydraulic fracturing is frequently performed to connect the wells and natural karst caves to enhance the oil/gas production. In this work, the mechanisms of connecting the caves through hydraulic fracturing are examined through experimentation, numerical modeling, and field observations. The experimental and numerical results show that three main connection modes exist for natural caves, specifically connections through straight main fractures, crooked main fractures, and pre-existing fractures, corresponding to connection modes I, II, and III, respectively. In the experiments, 6%, 17%, and 77% caves were noted to be connected through connecting modes I, II, and III, respectively. Connection mode III was the most effective, exhibiting a maximum angle value of 225°. When the geostress difference is large, few natural fractures are active, and the connection mode I/II frequently occurs. When the geostress difference ≤ 4 MPa, injection rate ≤ 10 ml/min, fracturing fluid viscosity ≤ 10 mPa s, a great number of natural fractures are active, and the connection mode III frequently occurs. Therefore, pre-existing fractures must be exploited to enhance the production of oil/gas in karst fracture-cavity reservoirs. Field observations indicated that by gradually injecting an acid fluid, the activated number of pre-existing fractures can be increased, thereby enhancing the efficiency of hydraulic fracturing and increasing the average daily oil/gas production.

Characterization of reservoirs, fluids, and productions from the Ordovician carbonate condensate field in the Tarim Basin, northwestern China

The TZ-No1 gas field in the Tarim Basin is the largest condensate field in China; however, it has not developed efficiently because of low and unpredictable production during the past 20 yr. Cores, logging interpretation, seismic descriptions, fluid properties, and production data indicate that this Ordovician carbonate field is different from conventional stratigraphic oil and gas fields as follows: (1) the hydrocarbon-bearing area covers a large region of 2000 km2; (2) matrix reservoirs have low porosity ( 20% per year). An examination of the carbonate reservoir and hydrocarbon accumulation history suggests that this large-scale stratigraphic accumulation formed during hydrocarbon emplacement in the early Paleozoic, with the reservoirs gradually evolving into tight reservoirs as a result of intense diagenesis. Variable amounts of Neogene gas charged the tight carbonate reservoirs and formed unconventional accumulations. The TZ-No1 gas field is characterized by a strongly heterogeneous tight matrix reservoir with a superimposed fracture-cave reservoir and a complicated unconventional fluid distribution, which provides insights into the exploitation challenges of unconventional carbonate resources.

Application of Geologically Constrained Machine Learning Method in Characterizing Paleokarst Reservoirs of Tarim Basin, China

As deep carbonate fracture-cavity paleokarst reservoirs are deeply buried and highly heterogeneous, and the responded seismic signals have weak amplitudes and low signal-to-noise ratios. Machine learning in seismic exploration provides a new perspective to solve the above problems, which is rapidly developing with compelling results. Applying machine learning algorithms directly on deep seismic signals or seismic attributes of deep carbonate fracture-cavity reservoirs without any prior knowledge constraints will result in wasted computation and reduce the accuracy. We propose a method of combining geological constraints and machine learning to describe deep carbonate fracture-cavity paleokarst reservoirs. By empirical mode decomposition, the time–frequency features of the seismic data are obtained and then a sensitive frequency is selected using geological prior constraints, which is input to fuzzy C-means cluster for characterizing the reservoir distribution. Application on Tahe oilfield data shows the potential of highlighting subtle geologic structures that might otherwise escape unnoticed by applying machine learning directly.

Design and construction of the knowledge base system for geological outfield cavities classifications: An example of the fracture-cavity reservoir outfield in Tarim basin, NW China

Tahe oilfield, located in NW Tarim Basin, is one of the largest and most difficult fracture cavity reservoirs in the world. Different fracture cavities, different generated mechanisms, and different oil production capacities. In order to study the significant parameters that can characterize the categories of facture-cavity. This research adopted outfield manual measurement, 3D digital modeling technique to obtain characterization parameters. According to experienced geological survey, typical outcrops were selected, then scanned by UAV (Unmanned aerial vehicle). Consequently, 3D digital models, including real coordinates and parameter information, were established by Agisoft Photoscan. Through geological testing results, various combination characteristic patterns of relative categories were analyzed. By using digital measure tool, combined with manually measured data, the parameters were extracted from the 3D digital model (DM). Then an initial geological database was established. For furtherly analyzing the database, the mathematic statistics methods of multiple linear regression (MLR), neural network technique (NNT) and discriminative classification technique (DCT) were applied. Using software of SPSS statistics 17.0, more than 200 groups of geological data (various categories of fracture-cavity) were optimally processed. Consequently, the significant characteristic parameters were interpreted to determine diverse categories. The results showed that: (1) cavity width, height, fracture length and cavity aspect ratio were significant parameters to classify runoff cavity categories. (2) Fault-controlled cavities could be accurately classified by fracture length and fracture density. (3) The main cavity categories could be distinguished by cavity width, cavity height and fracture density. Performances of the approach have been examined with 10 percentages of the samples, and a good agreement performed in the simulated results, and anastomosis rate was more than 80%. The researched results have critical guiding significance to evaluate types of fracture-cavity, develop and explore of fracture-cavity reservoirs. The construction technique of knowledge base can be applied for diverse fracture-cavity reservoirs in the various formations in different areas in the world.

Separating and imaging diffractions in dip domain on the basis of slope analysis

Fracture-cave reservoirs in carbonate rocks are characterized by a large difference in fracture and cavity size, and a sharp variation in lithology and velocity, thereby resulting in complex diffraction responses. Some small-scale fractures and caves cause weak diffraction energy and would be obscured by the continuous reflection layer in the imaging section, thereby making them difficult to identify. This paper develops a diffraction wave imaging method in the dip domain, which can improve the resolution of small-scale diffractors in the imaging section. Common imaging gathers (CIGs) in the dip domain are extracted by Gaussian beam migration. In accordance with the geometric differences of the diffraction being quasilinear and the reflection being quasiparabolic in the dip-domain CIGs, we use slope analysis technique to filter waves and use Hanning window function to improve the diffraction wave separation level. The diffraction dip-domain CIGs are stacked horizontally to obtain diffraction imaging results. Wavefield separation analysis and numerical modeling results show that the slope analysis method, together with Hanning window filtering, can better suppress noise to obtain the diffraction dip-domain CIGs, thereby improving the clarity of the diffractors in the diffraction imaging section.

Simulation of Mechanism of Hydraulic Fracture Propagation in Fracture-Cavity Reservoirs

Acid fracturing is a key measure to increase production of fracture-cavity reservoirs. Affected by the fracture-cavity system, hydraulic fractures will not propagate in a plane, and the mechanism of hydraulic fracture propagation is complicated. Therefore, considering the characteristics of hydraulic fracture propagation in fracture-cavity reservoirs, we established an extended finite element (XTEM) model for hydraulic fractures in fracture-cavity reservoirs. The simulation discussed hydraulic fracture extension in cases of a single cave and a single natural fracture and revealed the mechanism of dynamic propagation and extension of hydraulic fractures. The results indicated severe stress concentrations near caves, resulting in deflections of the fracture propagation direction. In the case of a single cave, upon shifts of shafts from the central line of the cave, the conditions of penetration of the cave by hydraulic fractures were investigated. It was shown that in the case of small approaching angles, the hydraulic fractures tend to deflect and join natural fractures; also, the hydraulic fractures can deflect and join natural fractures with large approaching angles and weak cementation. Generally small approaching angles and long natural fractures tend to induce hydraulic fractures and assist propagation towards the caves, thus increasing the probability of cave penetration.

Pre-stack Anisotropy Fractures Detection Based on OVT Domain Gather Data and Its Application in Ultra-deep Burial Carbonate Rocks

There are abundant fracture cave reservoirs wrapped in Ordovician tight limestone in the Tarim Basin, with an average buried depth of 7000m. The connectivity analysis of fracture-porous systems and hydrocarbon-bearing analysis has essential roles in the deployment of high-efficiency wells of the Ordovician carbonate reservoirs in the Tazhong and Tabei areas of Tarim Basin, as they are the major targets for increasing production. However, in the previous researches, the pre-stack fractures’ prediction and the oil/gas detection results using conventional processing data were lack of accuracy, which failed to complete the need of high-precision exploration and development. Firstly, the paper systematically analyzes the characteristics of azimuthal anisotropy analysis using conventional processing seismic data. Then it explains the process of selecting data, which is capable to meticulous reflect anisotropy characteristics of the formation and contains uniformed coverage to improve convergent results of elliptical fitting. Finally, the paper focuses on the three steps of operating azimuthal anisotropic pre-stack fracture detection using common reflection angle gather and receiving a reliable result. Practice demonstrates that using common reflection angle gathers during research of fractures in carbonate rock has a distinctive effect, which can provide a decisive basis for the layout of high-efficiency well groups in the development block.

利用试井双对数曲线计算缝洞型油藏动态储量的方法

利用试井双对数曲线计算缝洞型油藏动态储量的方法

Fluid prediction of a deep carbonate reservoir using walkaround 3D-3C vertical seismic profiling data

AbstractThe considerable depth and complicated structure of the Tahe Oilfield in the Tuofutai area of China make it very difficult to delineate its Ordovician carbonate fracture-cavity reservoir. The resolution of conventional ground seismic data is inadequate to satisfy current exploitation requirements. To further improve the understanding of the carbonate fracture-cavity reservoir of the Tahe Oilfield and to provide predictions of reservoir properties that are more accurate, a walkaround 3D-3C vertical seismic profiling (VSP) survey was conducted. First, we preprocessed raw VSP data and developed a method of joint PP- and PSV-wave prestack time migration. In contrast to ground seismic imaging profiles, VSP imaging profiles have a higher resolution and wider spectrum range that provide more detailed strata information. Then, using the joint PP- and PSV-wave prestack inversion method, we obtained the PP- and PSV-wave impedance and Poisson's ratio parameters of the Ordovician carbonate reservoir. Compared with the P-wave impedance of the ground seismic inversion, we found the VSP inversion results had higher accuracy, which enabled clearer identification of the internal characteristics of the carbonate reservoir. Finally, coupled with the Poisson's ratio attribute, we predicted the distribution of favorable reservoirs and interwell connectivity. The prediction results were verified using both logging and production data. The findings of this study demonstrate the applicability of the proposed technical method for the exploration of deep carbonate fracture-cavity reservoirs.

Fracture-cave carbonate reservoir permeability modelling based on conventional log and well deliverability predication: A case study of the Amu Darya Gas field in Turkmenistan

The carbonate fracture-cave reservoir is developing in carbonate gentle slope reef flat in east Amu Darya Gas field. Due to the serious heterogeneity of fracture-cave reservoirs, it is difficult to evaluate the productivity of different wells and different reservoir sections. Based on conventional log, core, image log and magnetic resonance log. The sensitive parameters contributed to reservoir permeability are studied, and the conventional log, magnetic log and image log of key well are set up to march core permeability and propagate other fracture-cave carbonate wells. Finally based on log porosity and permeability model result, the well deliverability is evaluated and the well deliverability evaluation results are match with the DST results. The Amu Darya Gas field carbonate fracture-cave permeability model and deliverability evaluation flowcharts and methods were build up and can give instructions for other fracture-cave carbonate reservoir.

Genesis and characteristics of the dolomite reservoirs in Middle Devonian Guanwushan Formation, Northwest Sichuan Basin, SW China

Abstract A great breakthrough has been made on oil-gas exploration of the Middle Devonian Guanwushan Formation in Northwest Sichuan Basin. The further exploration shows that the dolomite reservoir is complicated with insufficient investigation. Taking the Middle Devonian Guanwushan Formation as an example, systematic study has been carried out on its reservoir character, mechanism and genesis of dolostone. The field and core data suggest that reservoir types of Guanwushan Formation consist of crystalline dolomite, breccia dolomite and reef dolomite, and reservoir space is characterized by intercrystal (dissolution) pores, residual pores among breccias, intragranular dissolution pores, pockets as well as fractures. Besides, pore structure is of good configuration, showing medium-low porosity and moderate permeability, with average porosity and permeability of 2.23% and 0.44mD respectively, which suggesting fracture-pore and fracture-cavity reservoir. Combined with the previous research, it is suggested that the reservoir of Guanwushan Formation was controlled by facies, dolomitization and two-step karstification, with reef-shoal facies being material base for reservoir development, early dolomitization being key factor for reservoir space preservation, polyphase karstification being foundation for reservoir development and tectogenesis finally finalizing the reservoir.

Formation and preservation of a giant petroleum accumulation in superdeep carbonate reservoirs in the southern Halahatang oil field area, Tarim Basin, China

Giant petroleum accumulations worldwide with burial depths more than 7000 m (>23,000 ft) occur mostly in Mesozoic and Cenozoic reservoirs and yield predominantly natural gas. Recently, however, a giant oil accumulation with reservoir depths between 7000 m (23,000 ft) and 8000 m (26,000 ft) was discovered in the lower Paleozoic section in the southern part of the Halahatang region in the Tarim Basin, China. Petroleum sourced from lower Paleozoic rocks is contained in Ordovician karst fracture-cave reservoirs and sealed by Middle–Upper Ordovician limestones and mudstones. The newly discovered superdeep accumulation is among the deepest black single-phase oil accumulations worldwide and opens up new avenues for petroleum exploration in deep-marine carbonate reservoirs. Reservoir pressures are between 75 MPa (10,878 psi) and 85 MPa (12,328 psi), with pressure coefficients between 1.2 and 1.7 and temperatures ranging between 140°C (284°F) and 172°C (342°F). Charging and accumulation of petroleum occurred during the late Hercynian orogeny, followed by subsequent gradual deep burial, which took place before rapid subsidence beginning circa 5 Ma. Following subsidence, the thickness of overlying strata increased by more than 2000 m (>6600 ft) before finally attaining current depth. Therefore, this oil accumulation represents a well-preserved ancient petroleum system. Based on the geochemical features of oils and gases, the crude oils can be classified as mature, sourced from mixed marine organofacies of shale, marl, and carbonate, whereas the gases were cogenerated with oils. Despite very high present-day reservoir temperatures, no oil cracking has occurred because of the relatively short exposure of oils to high temperatures in a low geothermal gradient regime. Thus, there is significant exploration potential under similar conditions for liquid petroleum in superdeep strata. Faults and reservoirs are major factors controlling petroleum accumulation. Interlayer karsts with excellent fracture-cavity connectivity developed adjacent to faults, generally resulting in the enrichment of oil and gas along fault zones. High-quality reservoirs in this area are easy to identify because they exhibit strong bead-like amplitude features in seismic sections. Wells located near faults produce relatively large amounts of oil and gas. Effective karst fracture-cave reservoirs with noncracked oil may exist below 8000 m (26,000 ft) in the Tarim Basin and represent a significant exploration target in China.

Geochemistry of the fracture-cave calcite of the Ordovician Yingshan Formation and its paleokarst environment in the Tazhong area, Tarim Basin, China

The fracture-cave reservoir of the Yingshan Formation is an important oil and gas producing zone in the Tarim Basin. Karstification occurs at the top surface of the carbonate rocks of the Yingshan Formation on the northern slope of the Tazhong area due to a short exposure, so abundant fracture-cave spaces are formed. On the basis of the data of nearly 49 samples obtained from 21 wells, the carbon and oxygen isotopes of the fracture-cave calcite were analyzed. The carbon and oxygen stable isotopic characteristics recorded during paleokarstification were discussed to provide geochemical evidence for predicting the distribution of the fracture-cave reservoirs, as well as to understand the genetic mechanism of karst fracture-caves and the fluid properties and paleo-hydrological conditions of paleokarstification. The fracture-cave calcite can be divided into three types based on its carbon and oxygen isotope values, which indicate three types of paleokarst environments with different fluid properties. Type I calcite has similar carbon and oxygen isotope values to the bedrock of the Yingshan Formation, with δ13C values of − 2.0 to 1.1‰ and δ18O values of − 5.76 to − 8.16‰. These values indicate that the calcite was precipitated in the eogenetic karst environment of the Yingshan Formation. Type II calcite has a δ13C value of − 2.13 to 1.0‰ and a δ18O value of − 12.41 to − 8.0‰. It has a similar δ13C value, but a significantly negative oxygen isotope value compared with values of the bedrock of the Yingshan Formation, indicating a buried karst environment. Type III calcite has an extremely negative δ18O value (δ18O value < − 14.50‰), indicating hypothermal karst genesis. Its formation is related to magma or deep hydrothermal fluids. No calcite with atmospheric freshwater genesis and significantly negative δ13C and δ18O values was found in the samples, indicating that the formation of fracture-caves is weakly affected by atmospheric freshwater. The main reservoir space of the Yingshan Formation is karst caves. The calcite in the karst cave fillings belongs to type I, indicating an eogenetic karstification environment. Therefore, the formation of the fracture-cave reservoirs of the Yingshan Formation in the Tazhong area is related to eogenetic karstification, which occurred during exposure and mainly contributed to the formation of the reservoir spaces.

Grading evaluation and prediction of fracture-cavity reservoirs in Cambrian Longwangmiao Formation of Moxi area, Sichuan Basin, SW China

Abstract By using core, thin section, well logging, seismic, well testing and other data, the reservoir grading evaluation parameters were selected, the classification criterion considering multiple factors for carbonate reservoirs in this area were established, and the main factors affecting the development of high quality reservoir were determined. By employing Formation MicroScanner Image (FMI) logging fracture-cavity recognition technology and reservoir seismic waveform classification technology, the spatial distribution of reservoirs of all grades were predicted. On the basis of identifying four types of reservoir space developed in the study area by mercury injection experiment, a classification criterion was established using four reservoir grading evaluation parameters, median throat radius, effective porosity and effective permeability of fracture-cavity development zone, relationship between fracture and dissolution pore development and assemblage, and the reservoirs in the study area were classified into grade I high quality reservoir of fracture and cavity type, grade II average reservoir of fracture and porosity type, grade III poor reservoir of intergranular pore type. Based on the three main factors controlling the development of high quality reservoir, structural location, sedimentary facies and epigenesis, the distribution of the 3 grades reservoirs in each well area and formation were predicted using geophysical response and percolation characteristics. Follow-up drilling has confirmed that the classification evaluation standard and prediction methods established are effective.

Separating prestack diffractions with SVMF in the flattened shot domain

Abstract Separating weak diffractions in the prestack domain plays a vital role in high-resolution imaging small-scale discontinuities or inhomogeneities, which are associated with the migration paths and storage spaces for carbonate fracture-cave reservoirs. A shot-domain diffraction separation method is proposed with a SVMF (space-varying media filter) in the flattened shot domain. The diffractions with fast dynamic changings, including damping amplitudes and phase reversal, are filtered out by the spacing-varying median filter along the prediction-step directions of the flattened shot domain. The proposed method opens a possibility for separating diffractions in the shot domain and has an advantage in the traditional common-offset diffraction separation method. A numerical experiment illustrates the good performance of the proposed method in eliminating reflections and separating diffractions in the shot domain, and the field application further verifies its potential value in resolving the hidden small-scale cavities and tiny faults in carbonate reservoirs.

Experimental study on different water flooding methods for fractured-vuggy reservoir based on 3D printing

To study the distribution of residual oil after water flooding and the effectiveness of improved water flooding, the 3D printer was used to print the 3D model to imitate the fractured-vuggy reservoir modles of Tahe Oilfield. The purpose of this paper is to quantitatively describe the distribution of the remaining oil, study the mechanism of different improved water flooding methods, and provide theoretical support and technical support for further study of oil recovery. The experimental results of the three-dimensional model show that the remaining oil in such fracture-cavity reservoirs mainly exists at the top of the structure and the corners of the cave model, as well as the injection wells and the raised centers of the model.The remaining oil at the injection well can be produced after the injection-production inversion. After gas injection, the oil at the top of the model and the raised centers can be produced, indicating that changing the water flooding method can increase the oil production of the well.