Reservoir Description Research Articles

Application of CCUS in India: Designing a CO2 EOR and storage pilot in a mature field

Numerous mature oil and gas reservoirs around the world, along with added financial benefit, present a tremendous benefit of CO2 EOR and storage, especially in the regions where tax benefits and policies related to the CCS is limited. This work presents the first effort of CO2 EOR and storage in a mature oil field in India through a comprehensive application of laboratory study, reservoir static modeling, dynamic simulation, pilot design, and techno-economic sensitivity analyses. Through this case study, the technical feasibility of CO2 EOR and associated storage was assured for the first time through a novel approach of combining various subsurface and surface data with laboratory analyses. Almost no analog was available for CCUS on the same-age rock from a young thrust belt setting. The various vintages of core to seismic scale data posed a great challenge for effective integration. The solution approach to these issues included combining flow physics, fluid chemistry, geological concepts and digital modeling with practical engineering data analyses. Temporal change of oil composition in this reservoir due to the long production history had created some challenges for determination of CO2 miscibility. It was estimated through the lab study and modeling that the miscibility can be achieved near 3000 psi due to its altered oil composition resulted by years of production. To arrest the reservoir pressure decline, a pre-EOR water injection was identified as an immediately need to re-pressurize the reservoir and achieve miscibility of injected CO2. Comprehensive analysis of various subsurface and surface data integrating geoscience and engineering techniques have allowed for a consistent and applicable 3D description of reservoir, which was critical to identify suitable areas with appropriate remaining oil saturation, chemistry, and reservoir pressure. The history matching-calibrated-simulation model was utilized to evaluate the performance of various development scenarios of the identified area. Specifically, CO2 injection in a sector of geological model was performed using Todd-Longstaff miscible flood scheme. Upon comparing the proposed scenarios, a CO2 injection pilot in Pattern-1 was identified, with one injector and three producers over ∼60 acres area. This pilot uses 150 Metric Ton/day (MT/D) of CO2 captured and processed from an existing facility and transported about 70 km to the field location. The CO2 will be injected continuously into this pilot area for 5 years, and the well switches back to water injection afterward. Around 1.1 MMSTB incremental oil will be recovered in next 10 years, corresponding to 11.7% of OOIP in the flooded area. Up to 268,275 MT of CO2 will be sequestered in the reservoir. The learnings from this first ever study of its kind in India set the benchmark for data analysis, integration, and case specific approaches. The success and knowledge base from this endeavor will tremendously help and encourage further expansion of CCUS activities in India.

CE-SGAN: Classification enhancement semi-supervised generative adversarial network for lithology identification

Lithology identification, the process of recognizing and distinguishing lithology using specific methods, is a fundamental task in the fields of formation evaluation and reservoir description. However, the lithology identification accuracy of traditional models is insufficient because the distribution of small-sample logging data is usually extremely unbalanced. In this paper, a classification enhancement semi-supervised generative adversarial network (CE-SGAN) model is proposed to mitigate the influence of data imbalance and improve the lithology identification accuracy. Considering the powerful nonlinearity of logging curves, a classification separation architecture is applied to attain an optimal equilibrium between the classifier and the generator. Furthermore, a pseudo-label processing mechanism is designed to enhance classification, which combined with semi-supervised learning. Experiment results on two small sample logging datasets demonstrate that the model provides a considerable improvement in lithology identification. Moreover, it is competitive in data enhancement.

Middle platform carbonate depositional systems and lithofacies patterns in the Lower Ordovician Ellenburger Group, Tobosa Basin in West Texas, U.S.A., and subsequent Sauk-Tippecanoe megasequence boundary meteoric karsting

A long, continuous core (1155 ft; 352 m) from the Ellenburger Group in Upton County, Texas allowed for a detailed reservoir description of depositional setting, lithofacies, pore networks, and impact of subsequent karst processes on the reservoir geology. This reservoir description furthers the understanding of the origin and characteristics of pore types relevant for waste-water disposal, carbon dioxide storage, and hydrocarbon reservoir quality in the Ellenburger Group. The Lower Ordovician Ellenburger Group in West Texas is a thick dolomite sequence that was deposited on a broad shelf over a 16 m.y. Time period in the Tobosa Basin. The shallow-water restricted depositional setting produced carbonate sediments that are dominantly composed of middle-shelf microbial thrombolite boundstones and inner-shelf laminated (stromatolitic) mudstones. Recognizable skeletal grains are rare. The lower two thirds of the cored section in the area of investigation in Upton County, Texas is dominated by microbial thrombolite complexes with associated stromatactis features. Interbeds of oolites and evaporites are associated with the complexes and may represent small-scale fluctuations in relative sea level. Up-section, lithofacies transition into a peritidal complex composed of stromatolites and laminated mudstones, some displaying evaporite nodules. The lithofacies stacking pattern is similar to the regional established stacking pattern where the most open-marine lithofacies are at the base of the stratigraphic section and the most restricted lithofacies are at the top of the stratigraphic section. This consistent stacking pattern suggests a stable structural setting for millions of years where constant environmental conditions existed. Following deposition and subsequent lithification and dolomitization of the Ellenburger Group, the section underwent intense meteoric karsting (epigenic) during Late Middle Ordovician Sauk-Tippecanoe megasequence long-term exposure. The meteoric karsting affected the upper 700 ft (215 m) of the Ellenburger Group. The pore network in the studied core is composed of vuggy (small cavities) pores in the thrombolite lithofacies and crackle and mosaic breccia fracture pores and chaotic breccias interbreccia pores in karst-affected intervals. These pore systems support hydrocarbon production, waste-water disposal, and carbon-dioxide storage.

Profitable development technology of the Changning-Weiyuan National Shale Gas Demonstration Area in the Sichuan Basin and its enlightenment

Since the approval to establishment, the Changning-Weiyuan National Shale Gas Demonstration Area in the Sichuan Basin (hereinafter referred to as Demonstration Area) has been built up into a shale gas industry demonstration base characterized with scale, technology, management and green after more than 10 years of exploration and practice. Its successful experience is of great guiding significance to the efficient development of unconventional oil and gas resources in China. In this paper, the technologies which were developed for the beneficial development of the Demonstration Area during the 13th Five-Year Plan are systematically reviewed and summarized. Then, some countermeasures are proposed to solve the difficulties and challenges to the long-term benefit and stable production of middle-deep shale gas in this area. And the following research results are obtained. First, during the construction of the Demonstration Area, the “three-control” shale gas enrichment and high-production theory is innovatively proposed, and the shale gas enrichment model in the southern Sichuan Basin is clarified. Second, a high-production well cultivation method based on geology-engineering integration is established by developing six main technologies for shale gas exploration and development, which effectively supports the large-scale beneficial development of shale gas in the Demonstration Area. Third, the beneficial development model of middle-deep shale gas in the southern Sichuan Basin is preliminarily formed, and the benefit and efficiency of productivity construction are improved comprehensively. Fourth, the three measures of “controlling the decline rate, enhancing the reserve production and expanding the periphery” are used to support the replacement and stable production of middle-deep shale gas. In conclusion, to sustainably ensure the long-term benefit and stable production of shale gas in the southern Sichuan Basin, it is still necessary to deepen fine reservoir description and complex mechanism understanding and explore EOR technologies. What's more, the important mean to improve the single-well shale gas production rate in this area is to strengthen the fine fracturing design and implementation under the deep integration of geology and engineering and improve the construction quality of fracturing network continuously. Furthermore, the only way to the low-cost development of the demonstration area is to promote the management reform and innovation continuously and improve the beneficial development model further.

Lithofacies and electrofacies models for Mishrif Formation in West Qurna oilfield, Southern Iraq by deterministic and stochastic methods (comparison and analyzing)

In this study, the researchers attempted to build models that are more accurate by using lithofacies data along the field. Using a wider field area and extended data from both electrofacies and lithofacies could provide an accurate model of the reservoir description that will be useful for future field developments. The stochastic and deterministic models were presented to build the facies model as the basis for the construction, comparison, and selection of the more accurate model of the Mishrif Formation in the West Qurna oilfield/Iraq. The results obtained from this study indicated that the Sequential Gaussian indicator simulation algorithm offered a more accurate stochastic model between lithofacies data extracted from 20 wells and electrofacies from 75 wells, while the Truncated Gaussian simulation algorithm has a better match than others for the distribution percentage of lithofacies and electrofacies. The stochastic model shows that Mishrif Formation consists of approximately 35–40% as carbonates, 32–35% as shale, and 28–30% as coarse sand, Dolomite, and other materials according to the SISIM and GTSIM, while the deterministic by the kriging algorithm referred to as 62%, 24%, and 14%, respectively. The best variogram that gives the best results indicated that the direction of facies distribution is mainly South-North with an inclination to North-West.

From pilot knowledge via integrated reservoir characterization to utilization perspectives of deep geothermal reservoirs: the 3D model of Groß Schönebeck (North German Basin)

The Groß Schönebeck site in the North German Basin serves as research platform to study the geothermal potential of deeply buried Permian reservoir rocks and the technical feasibility of heat extraction. The structural setting of the site was investigated in more detail by a newly acquired 3D-seismic survey to improve the former conceptual model that was based on several old 2D seismic lines. The new data allow a revision of the geological interpretation, enabling the setup of a new reservoir model and providing base information for a possible further site development of Permo-Carboniferous targets. The 3D seismic allows for the first time a consistent geological interpretation and model parameterization of the well-studied geothermal site. Main reflector horizons and the corresponding stratigraphic units were mapped and the structural pattern of the subsurface presented in the 8 km × 8 km × 4 km large seismic volume. Attribute analysis revealed some fracture and fault patterns in the upper Zechstein and post-Permian units, while formerly hypothesized large offset faults are not present in the Rotliegend reservoir. However, a well-established graben-like structure at the top of the Zechstein succession is most likely related to broken anhydritic brittle intra-salt layers of some meter of thickness. Most reflectors above the salt show a rather undisturbed pattern. The main reservoir sandstone of the Dethlingen Formation (Rotliegend) was mapped and characterized. The base of the underlying Permo-Carboniferous volcanic rock sequence and hence its thickness could not be depicted reliably from the geophysical data. Based on the seismic data and the available reconnaissance drilling, logging, and laboratory data of the Groß Schönebeck research site, the thickness and distribution of the sedimentary Rotliegend (with emphasis of the sandy reservoir section) and of the volcanic rock sequence was modelled and stochastically parameterized with petrophysical properties guided by seismic facies pattern correlation, providing a more realistic reservoir description. Properties include total and effective porosity, permeability, bulk density, thermal conductivity, thermal diffusivity, and specific heat capacity. The data and interpretation constitute the basis for a better understanding of the thermo and hydromechanical processes at the site and for future measures. Further site development could include a deepening of one well to provide evidence on the volcanic rock sequence and consider deviated wells into favourable zones and the design of a fracture-dominated utilization approach.

Bayesian Framework Helps History Matching of Permian EOR Field With Data Uncertainty

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 200807, “Closing the Loop on a History Match for a Permian EOR Field With Relative Permeability Data Uncertainty,” by Usman Aslam, Emerson, and Jorge Burgos, SPE, and Craig Williams, Occidental Petroleum, et al. The paper has not been peer reviewed. _ Reservoir production forecasts are inherently uncertain because of the lack of quality data available to build predictive reservoir models. Traditionally, a best estimate for relative permeability data is assumed during the history-matching process despite significant uncertainty. Performing sensitivities around the best-estimate relative permeability case will cover only part of the uncertainty space. In the complete paper, the authors present an application of a Bayesian framework for uncertainty assessment and efficient history matching of a Permian carbon-dioxide (CO2) enhanced oil recovery field for reliable production forecasting. Field Details Regional and Structural Geology. The Central Basin Platform (CBP) is a positive tectonic feature that separates the Delaware and Midland sub-basins of the Permian. The study field is located on the northeastern end of the CBP, with the Permian (Guadalupian) -aged reservoir composed of San Andres Formation dolostone. The total thickness of the unit is approximately 1,500 ft, with the main reservoir within the middle 600 ft. Structural Framework. The area of interest features 270 wells that have a total depth in the San Andres formation or deeper. Of these, 234 have digital open- or cased-hole logs that were used to correlate formation tops. After reviewing all well logs, it became clear that, historically, the zones were primarily identifiable from porosity picks, which are more subjective than markers identified with gamma ray methods. A new sequence stratigraphic framework was developed based on core descriptions and outcrop analogs. This correlation framework was then extrapolated to well logs. After a grid of north/south and west/east cross sections was correlated across the field and a series of loop ties was made for quality-control purposes, structure and isopach maps were created for each zone. Reservoir Description. At the time of discovery, natural gas was trapped at the structural high point of the study field. Above the gas/oil interface is the gas cap. Below the gas was an oil accumulation, which extended to the producing oil/water contact (POWC). The POWC was defined by early drilling as the maximum depth where water-free oil was produced. The base of the transition zone is the top of the residual oil zone (ROZ); this reservoir interval extends to the free-water level and is an interval believed to have been waterflooded naturally. The ROZ is the target for CO2 injection. Grid Construction and Property Modeling. A full-field detailed 3D reservoir characterization was modeled at 50-ft × 50-ft grid increments and an approximate 2-ft average layer thickness. The reservoir model consists of 114,222,528 cells. A total of 235 wells in the unit area was correlated and used to constrain the structural framework of the model. Quantitative porosity log suites were available in 233 of the wells in the model area, which were used to create the full-field porosity property in the 3D model. The logs were normalized to the core data and upscaled.

Морфометрический анализ донного рельефа крупного долинного водохранилища в процессе его эволюции

Until now, the study of the morphology of the bottom of large reservoirs, subject to gradual siltation, received little attention. Morphometric descriptions of reservoirs are limited by the type, shape, altitude position, size of the bed, and the volume of water in them. The article presents the results of the analysis of the bottom relief of the Krasnodar Reservoir and the transformations of this relief for 2005–2021. The analysis was performed based on the materials of bathymetric surveys for the regulated volume of the reservoir on an area of 224 km2 with the construction of the corresponding digital relief models. The relief of the bottom of the reservoir is represented by flat areas of a flooded accumulative plain with prevailing slopes of about 0.2–0.4°, dissected by river channels of lower order tributaries. The transformation of the relief is caused by gradual siltation. The total volume of deposits for the specified area in 2005–2021 amounted to 127 million m3 with an average silt layer of 0.4 m. To describe the morphological properties of the bottom topography, we used geomorphometric techniques with the calculation of the BPI (Bathymetric Position Index) and the classification of mesoscale landforms based on it. For the bed, relief forms have been established related to three types of surfaces: flat (lower bank shelf), concave (depressions, deep depressions) and convex (reef crests, back reefs, mid-slope reefs). The constructed maps reflect the differentiated morphology of the bed surface, the evolution of landforms under conditions of continuous transformation of the basin, and also make it possible to judge the prevailing processes of morphogenesis. The coastal zone and the shallow part of the bed are the most complex in morphological terms. Here, along with reefs of different genesis, deep depressions and depressions in the form of underwater channels in advanced deltas can form on the accumulative shoal.

Analysis of development status and adjustment method of a block

Since a certain block was put into development, it has always put improving the injection production relationship and improving the ultimate recovery factor in the first place. Through a series of infill adjustment, supplement and extended drilling, the injection production relationship of single sand body has been gradually improved. In high water cut period, the remaining oil distribution has been quantified through joint multidisciplinary research, and the fluid production structure has been adjusted by combining the oil well injection, hole filling, drilling and other measures, Hard and stable production in high water cut stage is realized. However, due to the small scale of sand body development and fault development, the contradiction between single sand body injection and production is still prominent. From the perspective of development effect of Gaotaizi old area, compared with Xingnan development area, the degree of recovery at the same water bearing stage is obviously low, and the development effect is poor. At present, the comprehensive water cut has reached 92.77%, and the recovery percentage is only 28.05%. The research shall be based on the results of fine reservoir description, guided by the results of multidisciplinary research, and focus on the comprehensive analysis and sorting of the injection production relationship of single sand body through the re understanding of geology, so as to find the adjustment potential of supplement and injection conversion. Through the adjustment of the injection production system, increase the water injection well points, expand the swept volume, improve the degree of water drive control, so as to increase the formation pressure and improve the development effect of the block.

Discussion on reservoir description method of well vibration combined with tight well pattern area

In the process of rapid social and economic development, the demand for the oil of related industries is more and more large. The continuous increase of oil exploitation is causing some oil fields to gradually enter the period of special high water cut development and increasing the difficulty of oil exploitation. Therefore, how to improve oil recovery is the key question that relevant personnel think and solve. Based on this, this paper mainly describes the channel sand body description technology combined with well shock, and analyzes the reservoir description method combined with well shock combined with the general situation of an oilfield working area, aiming at improving the prediction accuracy of sand body in dense well pattern area and effectively guiding the development and adjustment of potential excavation work.

An Effective Thin Reservoir Identification Method for Fine Oilfield Development

Thin reservoirs prediction method such as spectral inversion has drawn considerable attention in recent years. In order to avoid extracting wavelets within the whole field area purposeless and to make the filtered data has preferable fidelity as well as signal-to-noise ratio, an effective structural constrained thin reservoir description method which combines spectral inversion and wide-band Ricker wavelet filtering technology has been proposed in this paper. The method given here is more credible and is suitable for the prediction of middle-deep thin reservoirs. We take LD-A structure within Bohai Bay Basin as an example to show the implement of our method. Several sets of thin sand layers which are hardly to recognize originally have been finally identified. Also, with the application of this method, a high-production thin reservoir of LD-B structure has been identified accurately, which provides credible information for subsequent fine oil exploration and development.

Using 3-D seismic data to estimate stress based on the curvature attribute integrated mechanical earth model

SUMMARY The current state of the technology for unconventional gas and oil development integrates geology, geophysics and engineering into a comprehensive reservoir description. To construct a mechanical earth model (MEM) which takes the geological structure influence into account, we introduce the curvature attribute to express the horizontal strains and extend the classical uniform horizontal strains MEM. The horizontal strains are derived based on the theory of plates and depend on the curvature attributes which reflect the geological structure influence. To take seismic data into the unconventional reservoir characterization, we design a geophysical workflow to estimate the in-situ stress. Amplitude Versus Offset (AVO) inversion produces the elastic parameters and the finite-difference method calculates the curvature attributes. The Bowers’ method computes the pore pressure and the in-situ stresses computed from the well-log data are used for the calibration. Real data from the shale gas pilot development areas in the Zhaotong National Demonstration Zone are used to demonstrate the method and compare the new MEM results with the MEM modelling technique results. The curvature attribute integrated MEM shows its advantage.

Model-data-driven P-wave impedance inversion using ResNets and the normalized zero-lag cross-correlation objective function

Model-driven and data-driven inversions are two prominent methods for obtaining P-wave impedance, which is significant in reservoir description and identification. Based on proper initial models, most model-driven methods primarily use the limited frequency bandwidth information of seismic data and can invert P-wave impedance with high accuracy, but not high resolution. Conventional data-driven methods mainly employ the information from well-log data and can provide high-accuracy and high-resolution P-wave impedance owing to the superior nonlinear curve fitting capacity of neural networks. However, these methods require a significant number of training samples, which are frequently insufficient. To obtain P-wave impedance with both high accuracy and high resolution, we propose a model-data-driven inversion method using ResNets and the normalized zero-lag cross-correlation objective function which is effective for avoiding local minima and suppressing random noise. By using initial models and training samples, the proposed model-data-driven method can invert P-wave impedance with satisfactory accuracy and resolution. Tests on synthetic and field data demonstrate the proposed method's efficacy and practicability.

Petroleum Geology and Exploration of Deep-Seated Volcanic Condensate Gas Reservoir around the Penyijingxi Sag in the Junggar Basin

Many types of volcanic rock oil and gas reservoirs have been found in China, showing great petroleum exploration potential. Volcanic reservoir also is one of the key fields of exploration in the Junggar Basin and mainly concentrated in the middle and shallow layers, while the deep volcanic rock and natural gas fields have not been broken through. Based on comprehensive analysis of core observation, single well analysis, reservoir description, source rocks evaluation, combined with seismic data and time-frequency electromagnetic technology, multiple volcanic rock exploration targets were identified, and industrial oil and gas flow was obtained in the well SX 16 of the Penyijingxi Sag, western Junggar Basin. It is believed that the deep Permian source rocks have relatively higher natural gas generation potential and volcanic breccia usually have large reservoir space. And the mudstone of the Upper Wuerhe Formation played as the role of caprock. The success of exploration well SX16 has achieved a major breakthrough in natural gas exploration in the Penyijingxi Sag, which has essential guiding significance for the exploration of deep volcanic rocks and large-scale gas exploration in the Junggar Basin.

Characteristics and Seismic Identification Mode of Ultra-Deep Carbonate Fault-Controlled Reservoir in Northwest China

Ordovician carbonate reservoirs in the Shunbei area of the Tarim Basin are characterized by large burial depth, small vertical fault displacement of the strike-slip fault zone, small karst development scale, strong reservoir heterogeneity, complex and diverse seismic reflection types, which lead to unclear seismic response characteristics of fault zone and reservoir, and further restrict the fine description of ultra-deep (>7300 m) fault controlled reservoirs. On the basis of high-precision 3D seismic data analysis, combined with drilling, logging, and comprehensive geological interpretation data in the Shunbei area, seismic geological models of different types of reservoirs and fault zones are established. The changes in seismic response characteristics of fault zones and reservoirs are simulated and analyzed by changing reservoir size, scale, fault and fracture cavity combination modes, as well as other factors. On this basis, two seismic identification models of fault-controlled reservoirs in the Shunbei area are summarized and established. The seismic identification mode of seismic reflection marker wave of fault-controlled reservoir is mainly “fault seismic response characteristics & weak reflection” and red trough anomaly under T74. The internal seismic identification modes are mainly “fault seismic response characteristics & random reflection”, “fault seismic response characteristics & beading”, “fault seismic response characteristics & linear weak reflection”, and “fault seismic response characteristics & random reflection”. Among them, except for “fault seismic response characteristics & random reflection”, the coincidence rate of reservoir prediction of other three types of seismic response characteristics is more than 70%. The coincidence rate of the other three types of seismic response characteristics of a reservoir is more than 70%. The research results provide a reference for the prediction and description of ultra-deep carbonate fault-controlled reservoirs.

Integrated Deep-Learning and Physics-Based Models Improve Production Prediction

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204864, “Integrating Deep-Learning and Physics-Based Models for Improved Production Prediction in Unconventional Reservoirs,” by Syamil M. Razak, SPE, Jodel Cornelio, SPE, and Atefeh Jahandideh, SPE, University of Southern California, et al. The paper has not been peer reviewed. _ The physics of fluid flow and transport processes in hydraulically fractured unconventional reservoirs is not well understood. As a result, predicted production behavior using conventional simulation often does not agree with observed field performance data. The discrepancy is caused by potential errors in the simulation model and the physical processes that take place in complex fractured rocks subjected to hydraulic fracturing. In the complete paper, the authors discuss the development of a deep-learning model to investigate the errors in simulation-based performance prediction in unconventional reservoirs. Introduction One of the major challenges for petroleum engineers working with unconventional reservoirs is a lack of models that accurately represent a physical relationship between the formation, completion and fluid properties, and production responses. Statistical predictive models typically are used to extract sets of input parameters that better represent the properties of the field. However, a major drawback with statistical models is their inability to extrapolate from the training data set. The authors propose a deep-learning predictive model based on a combination of physics and data to account for the errors that may have come from undiscovered physics or imperfect description of unconventional reservoirs. The model leverages the power of deep learning to account for systematic prediction inaccuracies resulting from incomplete knowledge about the reservoir model and the underlying flow processes. Deep neural network models trained with observed production responses and other related data in the field are used to enhance the prediction performance of simulation models with limited knowledge of flow physics in complex, unconventional reservoirs. The data the authors use for their model consist of the following: - Formation, completion, and fluid properties for physics-based reservoir simulation (xsim) - Corresponding simulated production responses (dsim) - Formation, completion, and fluid properties collected from the field (xfield) - Related observed production response data (dfield) The authors define simulation errors (derr) as the difference between dsim and dfield. Each derr is paired with xerr that is the concatenation of the corresponding xsim and xfield. The predictive model integrates a 1D convolutional autoencoder (AE) that extracts temporal trends in the simulation errors as a set of latent variables. These components are used to train deep regression neural networks to represent the complex relationship between the simulation errors and these latent variables.

The Advances and Challenges of the Ediacaran Fractured Reservoir Development in the Central Sichuan Basin, China

The largest Precambrian gasfield in China has been found in the central Sichuan Basin. It has been assumed as an Ediacaran (Sinian) mound–shoal, microfacies-controlled, dolomite reservoir. However, the extremely low porosity–permeability and heterogeneous reservoir cannot establish high production by conventional development technology in the deep subsurface. For this contribution, we carried out development tests on the fractured reservoir by seismic reservoir description and horizontal well drilling. New advances have been made in recent years: (1) the prestack time and depth migration processing provides better seismic data for strike-slip fault identification; (2) seismic planar strike-slip structures (e.g., en échelon/oblique faults) and lithofacies offset together with sectional vertical fault reflection and flower structure are favorable for strike–slip fault identification; (3) in addition to coherence, maximum likelihood and steerable pyramid attributes can be used to identify small strike-slip faults and for fault mapping; (4) fusion attributes of seismic illumination and structural tensor were used to find fractured reservoir along fault damage zone; (5) horizontal wells were carried out across the strike-slip fault damage zone and penetrated fractured reservoir with high production. Subsequently, a large strike-slip fault system has been found throughout the central intracratonic basin, and the “sweet spot” of the fractured reservoir along the strike-slip fault damage zone is widely developed to be a new favorable domain for high-production development. There is still a big challenge in seismic and horizontal well technology for the economical exploitation of the deep fractured reservoirs. This practice provides new insight in the deep tight matrix reservoir development.

A Plasma Transmitting Source for Borehole Acoustic Reflection Imaging.

The detection depth of current borehole acoustic reflection imaging is only tens of meters without high resolution. This considerably limits its wide application in the identification and fine description of unconventional reservoirs and in the optimization of drilling trajectories. Increasing the directional energy from the transmitter to a geological structure is an excellent way to solve this issue. In this study, a plasma source with a parabolic reflector was introduced during borehole acoustic reflection imaging. First, an experimental system was built for testing the plasma source. Next, the acoustic-electrical characteristics and directional radiation of the source were studied using experiments and a numerical simulation. Finally, the advantages, disadvantages, and feasibility of the plasma-transmitting source were analyzed; some suggestions for further work on the source and its logging application were proposed. The experimental and simulation results show that the use of a plasma source with a parabolic reflector can increase the detection depth of borehole acoustic reflection imaging to hundreds of meters with high resolution. This is crucial in imaging the geological structures near boreholes and enhancing oil–gas exploration and development.

Reservoir Description, Diagenesis and Reservoir Quality of the Deep Marine Sediments in the Propagation Stage of Rift Basin

The exploration and exploitation of the downthrown side of the productive upthrown Pre-rifting reservoirs at the Gulf of Suez marked bring a renaissance to the rift basin Exploration. This work documents the reservoir performance, trap geometry, and structural style of the downthrown deep marine stratigraphic entrapment. In addition, it outlines the requirements necessary beyond the production mitigations and limits. To gain better understanding of Asl Formation (deep marine) reservoir characteristics early in the exploration program, Asl Formation was cored in the north October J-5 well. A continuous 366- foot (112m) core was recovered including the main reservoir interval, which is producing over 12,000 barrel of oil per day. The J-5 Asl Formation has been interpreted as a synthetic, mixed clastic-carbonate turbidity deposit. Three major lithofacies described are recognizable on electric log. These are sandstone, shale and carbonates. The sandstones dominate the lower portion of the core and are the main oil producing section. Sandstone porosity and permeability range from 17 to 27% and 30 millidarcies to 3 darcies, respectively. Compared to the sandstone, the carbonate turbidites have poorer reservoir quality. They dominate the upper portion of the core and are composed of coarse fossil debris, silica framework grains and rock fragments. Horizontal and vertical permeabilities with rock types. Both the sandstone and carbonate sections of the J-5 core have experienced a complex diagenetic history. Deposition of the cored interval was initiated by a convulsive geological event such as flashflood or earthquake. These events would likely generate sufficient energy for mobilization of onshore and/or near shore sediments into multiple gravity flows having regional extent. The reservoir quality is controlled by a combination of primary depositional fabric and subsequent diagenetic modification. This research work can guide future exploration of reservoir-prone deep marine deposits in the Red Sea Rift and provide a reference for the subsurface deep-water reservoir quality analysis in the propagation stage in the Rift Basins.

The Advancement and Challenges of Seismic Techniques for Ultra-Deep Carbonate Reservoir Exploitation in the Tarim Basin of Northwestern China

The largest ultra-deep (>6000 m) strike-slip fault-controlled oilfield in the world is found in the Tarim Basin of Northwestern China. The localized fractured reservoirs are the major production targets along the strike-slip fault zones. Different from its use in the primary porous-type reservoirs, however, the conventional technology is not favorable for use in oil/gas development in Ordovician carbonate reservoirs. For this reason, high-density seismic acquisition and high-resolution seismic processing were carried out to provide high-precision data for fault and fractured reservoir identification. In addition, the multi-filtering process and the maximum likelihood method are typically used to identify small faults and fault segments along a strike-slip fault zone. Further, seismic facies-constrained inversion and amplitude attributes are favorable for large fracture-cave reservoir description. With the advancements in seismic technology, the high and stable production well ratio has been doubled in the “sweet spots” of fractured reservoir optimization, and the first ultra-deep strike-slip fault-controlled oilfield with an annual oil production of over 1 million tons has been realized, achieving economic development in the ultra-deep fractured reservoirs. However, unstable production and high rates of production decline are still significant challenges in the economic exploitation of the ultra-deep fractured reservoirs. Seismic technology requires further improvement for the description of small fractured reservoirs and matrix reservoirs, as well as reservoir connectivity prediction and hydrocarbon detection in the deep subsurface.