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Carbonate reservoir is the focus of oil and gas exploration and also the subject of much research in the world. High-yield industrial oil and gas flow has been found in the fault-controlled carbonate reservoirs of the Middle Lower Ordovician in the Shunbei area. In the process of drilling and development, this type of reservoir faces many problems closely related to the current stress state, which need to be solved urgently. In this paper, the direction of the maximum horizontal principal stress is determined by using the global positioning system (GPS), the azimuth of fast shear wave propagation, and borehole enlargement. In addition, under the calibration of acoustic emission experiment results, cross-dipole logging data are used to evaluate the in situ stress in the study area. According to the results of the rock mechanics experiment and logging interpretation, the conversion relationship between dynamic and static parameters of rock mechanics is established. Finally, according to the fault and horizon interpreted by 3D seismic data, a 3D geological model of the study area is established. Under the constraint of logging interpretation and experimental results, the stress field in the study area is simulated by the iterative boundary element method. The simulation results show that the distribution of the in situ stress field is affected by the arrangement of faults. From the map view, it shows the segmentation along the fault strike; that is, different segments show different characteristics. In the vicinity of strike-slip faults, the principal stress direction is deflected to varying degrees. The relative error between the simulated value and the measured value is less than 10%, which verifies the reliability of the numerical simulation results. The research results can provide a reference for the determination of optimal mud weights, the optimization of wellbore trajectory, and the selection of acid fracturing operation parameters. [ABSTRACT FROM AUTHOR]

The Gulf of Suez in Egypt contains more than 80 conventional oil fields with reservoirs from Precambrian up to Quaternary age. To date, these fields have all been conventional resources. This abstract will take part of the Gulf of Suez sequence within the fields of Petrogulf Misr Company and present a work process for unconventional resource assessment of the Brown Limestone formation within one of these areas. The Brown Limestone formation is a Late Cretaceous Pre-rift mega sequence succession and plays an important role in the conventional system of Gulf of Suez, Brown Limestone formation is not only as one of the important source rocks, but also a fractured carbonate reservoir in multiple fields especially is the southern Geisum oil field. However, this formation is characterized by uncertainty due to the complexity of reservoir architecture, various lithologies, lateral facies variations, and heterogeneous reservoir quality. These reservoir challenges, in turn, affect the effectiveness of further exploitation of this reservoir along the Gulf of Suez Basin. In this work, we conduct an integrated study using multidisciplinary datasets and techniques to determine the precise structural, petrophysical, and facies characteristics of the Brown Limestone Formation and predict their complex geometry in 3D space. The Brown Limestone formation is considered to be as a reservoir in the study area. The value of water saturation ranges from 15 to 45%, where the value of Effective Porosity ranges from 11 to 15% for the selected potential intervals in Brown Limestone due to the highly structural setting in the study area, so Reservoir thickness was used as the proxy for reservoir effectiveness where thicker reservoir had a higher chance of containing multiple intervals for good potential intervals. [ABSTRACT FROM AUTHOR]

For evaluation of heterogeneity in reservoir rocks, different data and various methods have been proposed. The routine rock typing methods are one of these, but the accuracy of the separated rock types is still under discussion. The purpose of this study is the accurate measurement of 6 routine rock typing methods using standard error, coefficient of variation, and coefficient of determination parameters. Such an assessment leads to identification of rock typing methods in which the units are less heterogeneous. For this, a total of 1576 plugs and RCAL data from 402.6 m of Dalan and Kangan formations of one well in the central part of the Persian Gulf have been analyzed. The rock typing methods include flow zone indicator, current zone indicator, Lucia rock fabric numbers, Lorenz plot, Winland R35, and microfacies grouping. The accuracy of each rock types in 6 methods was measured by the mentioned statistical parameters. Also, the effect of quantified geological processes used in the heterogeneity evaluation of each rock types. In the rock types obtained from flow zone indicator by normal probability plot, all three statistical values indicate lower heterogeneity compared to other methods. We obtained higher values of coefficient of determination and lower values of standard error and coefficient of variation in the flow zone indicator method, which are due to the direct effects of porosity and permeability on the flow zone indicator formula and using normal probability plot method. Also, geologically, dolomitization had homogenized the porosity and permeability distribution in the studied formations. [ABSTRACT FROM AUTHOR]

The limestone reservoir beds of Late Ordovician Lianglitage Formation are preserved in northwestern Tazhong Uplift of the Tarim Basin with buried depth exceeding 6000 m. The origin of the ultra-deep limestone reservoir is still controversial, which restricts the further hydrocarbon exploration. In order to clarify the main controlling factors of reservoirs, we carried out the study of sedimentary facies, diagenesis, and reservoir characteristics based on seismic, well logging, and core data. The Lianglitage Formation in northwestern Tazhong Uplift is mainly composed of nine lithofacies that are deposited from platform margin reef-shoal, platform-interior shoal, and restricted lagoon to tidal flat environments. The Lianglitage Formation has experienced syndepositional submarine diagenesis, penecontemporaneous diagenesis, and burial diagenesis, and consequently the reservoir space in the formation mainly includes fractures and dissolution vugs and caves. Reef and shoal deposits are the material basis of favorable reservoirs, and the favorable reservoirs have been mostly improved by the dissolution of meteoric water in penecontemporaneous diagenesis. In the burial stage, the early-formed porosity was destroyed by cementation to some extent, but the fractures and associated vugs formed in the late Ordovician and Silurian-Devonian played an important role in the improvement of the reservoir. The results are of great significance to the prediction of deep carbonate reservoirs and the hydrocarbon exploration in basins of western China. Favorable facies, early-stage improvement by meteoric water, and tectonic fracture are key to the formation of high-quality large-scale deep limestone reservoirs. [ABSTRACT FROM AUTHOR]

Seismic facies analysis (SFA) has been proven to be useful in interpreting seismic data, allowing significant information about subsurface geological structures to be extracted. SFA uses different seismic attributes extracted from 3D seismic data and well logs to construct detailed seismic facies and lithology variation maps. Accurate seismic facies map could be used for reservoir exploration, optimization, management, and development. The recent SFA research was mainly based on unsupervised methods, with few works done using supervised classification. Therefore, this study focuses on supervised classification for qualitative mapping of the reservoir facies distribution. Precisely five well-known classifiers, called the multilayer perceptrons (MLPs), support vector classifier (SVC), Fisher, Parzen, and K-nearest neighbor (KNN). Each classifier was tested to provide an opportunity for the direct assessment of their feasibility in the classification of facies. The approach was applied on the carbonate reservoir from a real oil field in Iran. The numerical relative errors associated with different classifiers as a proxy for robustness of SFA provides reliable interpretations. Our results show stability of both SVC and MLP classifiers in supervised-classification-based studies although SVC has relatively better results. [ABSTRACT FROM AUTHOR]

A microseismic experiment utilizing a single downhole array of eight 3-component receivers was conducted in an offshore oilfield in the emirate of Abu Dhabi in the United Arab Emirates. The Lower Cretaceous Thamama Group is the major carbonate reservoir in the field producing from six zones. Microseismic data was acquired in conjunction with gas injections that took place in the Thamama IV A and IV B reservoirs during 9 days of acquisition. The aim of the experiment was to monitor the microseismic activity arising in the carbonate reservoirs as a result of gas injection. A total of 103 microseismic events were detected from two of the receivers. For the majority of these events, there were no well-defined P wave arrivals, probably due to the presence of strong background noise and the very weak microseismic signals. The results from this experiment indicate that the detected events are probably related to the microseismic activities caused by the gas injection within the Thamama IV B reservoir. Therefore, downhole microseismic monitoring methods can potentially provide valuable information about the fracture systems within the carbonate reservoirs of Abu Dhabi's oilfields. [ABSTRACT FROM AUTHOR]