Electric Logs Research Articles

Biostratigraphy v. geophysics; correlation of Middle Turonian chalks in the Anglo-Paris Basin

High-resolution correlations between boreholes are commonly based on a combination of geophysical well-log data and biostratigraphy, and when these conflict resolution can be contentious and difficult. Such a situation exists in the Middle Turonian chalks of the Anglo-Paris Basin, where electrical resistivity logs, registering thin but seemingly laterally continuous beds of clay-rich chalk (marls) in mostly uncored boreholes, provide apparently straightforward correlations across broad regions. In contrast, detailed biostratigraphical analysis using microcrinoids provides very different results, showing the presence of a major hiatus associated with a hardground and differing significantly from the geophysical correlations. Detailed re-examination of this contentious problem, utilizing exposures adjacent to boreholes, demonstrates the supremacy of detailed biostratigraphical analysis, independently supported by regional thickness patterns, cyclostratigraphy and geochemistry. Although closely spaced geophysical well logs can afford convincing correlations, their use in correlation over broader geographical regions leads to erroneous and misleading conclusions.

Evaluation and engineering applications of the in situ stress state of deep tight sandstone reservoirs in the Xujiahe Formation of the Yingshan-Longgang in the central Sichuan Basin

Introduction: The Xujiahe Formation in the Yingshan-Longgang area of the Sichuan Basin has abundant tight oil and gas resources. However, the complex geological conditions and insufficient understanding of the magnitude and direction of in-situ stresses severely limit exploration and development of oil and gas resources in the region. This has made it difficult to carry out hydraulic fracturing and horizontal well deployment in the region.Methods: Based on experimental analyses, including acoustic emission experiments, wave velocity anisotropy experiments, and paleomagnetic experiments, this study evaluated the magnitude and direction of in-situ stresses, while also combining electrical imaging logging and acoustic wave logging data. This provides a basis for hydraulic fracturing in the research area.Results and Discussion: The experimental results indicate that the three-way stress state of the Xujiahe Formation is a strike-slip stress state, and the three-way stress value gradually increases with increasing burial depth. The Longgang area is particularly affected by the depth. The average azimuth angle of the maximum horizontal principal stress in the study area is N100°E, while tectonic deformation may cause a counterclockwise deviation of the maximum horizontal principal stress azimuth in the Yingshan area. Considering the influence of changes in the magnitude of in situ stress in the longitudinal direction on hydraulic fracturing extension mode, it is recommended to select the middle and upper sections of the Xu II for fracturing and transformation. Similarly, considering the distribution of natural fractures and the direction of the in situ stresses, it is suggested that the deployment azimuth angle for horizontal wells be between N20°–30°E.

Advanced Diagnostics Aid Understanding at Hydraulic Fracturing Test Site 2

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 2021-5514, “Overview of Hydraulic Fracturing Test Site 2 in the Permian Delaware Basin (HFTS-2),” by Jordan Ciezobka, SPE, GTI. The paper has not been peer reviewed. _ The Hydraulic Fracturing Test Site 2 (HFTS-2) is a large collaborative field-based research and development program in the Permian Delaware Basin funded by the US Department of Energy through the National Energy Technology Laboratory and the exploration and production industry with support from academia. The project’s main objective is to improve the understanding of the hydraulic fracturing process through use of advanced diagnostics and collection of through-fracture cores to provide undisputable evidence and attributes of created fractures. Project Background The HFTS-2 project provides the opportunity to address the optimal development of a stacked pay resource that requires simultaneous drilling and completion of tens of thousands of wells across multiple geologic horizons, also known as cube development. The project consists of a series of coupled analytic and field experiments in which research-quality data are acquired in dedicated research wells through full instrumentation at, and in proximity to, hydraulically fractured wells. Furthermore, the unique site design provides an opportunity to understand the effect of reservoir depletion because many child-well stages overlap parent-well areas. The extensive data set acquired was integrated and used to calibrate subsurface models and characterize fracture geometry and proppant distribution. Diagnostics and modeling efforts enabled comprehensive calculations of hydraulic fracturing’s vertical and lateral extent and production-depletion profiles and quantification of fracture growth bias for child-well stages that overlapped parent wells. Results from the project culminated in the development of a series of optimization procedures for increased drilling and completion efficiency, reducing environmental footprint by producing the reservoir from fewer well pads and fracturing stages. Test Site The research well package consists of eight new producing wells, two existing parent wells, and two new dedicated science and observation wells drilled for this project. The new producing wells are landed in various Wolfcamp horizons and have lateral lengths of approximately 7,500 ft. The lateral sections of the wells are spaced approximately 660 ft apart. The two existing parent wells also are in the Wolfcamp formation and have lateral lengths of approximately 5,000 ft. The two new science wells were drilled from the same pad, positioned between laterals B3H and B4H. One science well is a vertical pilot hole used to characterize the reservoir through the collection of mud and drill-cutting samples, electric logs, and whole and sidewall cores. The well also was used to house diagnostic instrumentation. The second science well is a slant well drilled after all wells were stimulated and was used to collect whole cores through the created fractures. The slant core well was instrumented with pressure and temperature gauges to monitor reservoir depletion during production.

Cyclostratigraphy at a tipping point

There are key patterns of variation in the (litho‐) stratigraphical record, which, with advances in computing technology in recent decades, have become amenable to objective numerical analysis. This research has chiefly focused on the search for spatially regular cycles in the sedimentary rock record, since there are theoretical grounds for believing that these would be periodic and thus provide a means of time‐calibrating the stratigraphical records in which they occurred. Less popular lines of research consider the scaling relationships of the tangible, measurable sedimentary rock layers, and of the hiatuses, individually of indeterminate length, that punctuate these layers. Objective source data for all these analyses is provided, on limited (usually decametre) scales, by detailed lithological logging, sampling and dating of sections provided by exposures and cores. An objective global lithostratigraphical database, with larger, kilometre scales, is provided by the widespread practice of electric (wire‐line) logging of deep wells. This involves measurement, at 6‐inch (~15 cm) depth intervals of lithology‐related petrophysical properties. Rapid desk top computer analysis of the hundreds or thousands of readings that comprise these two data series, searches for patterns of variation. This review considers the published evidence for ‘ubiquitous’ cyclicity and its use in chronostratigraphy, despite the contrary claims that stratigraphical records are predominantly random in character.

Dolomite reservoir fluid discrimination method based on fluid identification factor

The complexity of the pore structure of dolomite leads to strong heterogeneity of the reservoir distribution and the inability to accurately describe the rock-electric parameters, which makes it difficult to distinguish the properties of reservoir fluids based on electrical logging. In this paper, fluid identification factors are applied to dolomite reservoirs for the first time, which enriches the methods of non-electric logging to identify reservoir fluid properties. Based on the inductive analysis of existing fluid identification factors, according to the number of times that logging data participates in the calculation, they are divided into three types of fluid identification factors: direct, indirect and composite; composite fluid identification factors can reflect changes in reservoir lithology, and reconstruct composite fluid identification factor H considering the difference between the lateral deformation coefficient of dolomite and other lithologies; the sensitivity of the composite fluid identification factor to gas saturation is tested, and fluid factors used in dolomite reservoirs were optimized. Select the array acoustic logging and density logging data from three wells in the subsalt dolomite in the Tarim Basin, China, calculate the parameters of the compressional wave and shear wave impedances (Ip, Is), λρ, μρ, ρf, F, H and etc., and use the two-dimensional chart method to analyze the effect of the fluid identification factors above, and λρ-μρ, F-σ, ρf-σ, H-μ and other charts are selected to establish logging fluid discriminant curves. The application shows that the fluid identification factor H is more suitable for distinguishing gas layers, and F is more suitable for distinguishing water layers.

Prediction of lithology in lacustrine carbonates using well logs: The Cretaceous Barra Velha Formation in Santos Basin, offshore Brazil

Abundant hydrocarbons have been produced from the pre‐salt lacustrine carbonates of the Cretaceous Barra Velha Formation in the Santos Basin of offshore Brazil. The highly heterogeneous lithology and pore systems make it difficult to predict the reservoir quality via petrophysical well logs. Core description, computed tomography (CT) scanning, thin sections and wireline well logs are utilized to characterize the lithology, pore spaces are reservoir quality of the Cretaceous Barra Velha Formation pre‐salt lacustrine carbonates in the Santos Basin. The results show that the lithology mainly includes shrubstone, grainstone, laminated micrite and massive micrite. The pore systems are dominated by secondary pores, such as intergranular pores, dissolution pores and intercrystalline pores as well as modified primary pores. Geological well logs (conventional well logs, electrical and sonic image logs and nuclear magnetic resonance [NMR] logs) are integrated to build the predictable models of the carbonate reservoirs. The shrubstone, which is dominated by intergranular pores, has the highest reservoir quality, which can be derived from NMR logs. Grainstone contains both primary intergranular pores and abundant secondary dissolution pores. The laminated and massive micrite contain only micropores and therefore have the lowest reservoir quality. Lastly, conventional well logs integrated with electrical and sonic image logs are utilized to predict the distribution of lithology and reservoir quality in single wells, and the results are testified by the NMR log data. The shrubstone and grainstone are future exploration targets of the Cretaceous Barra Velha Formation in the Santos Basin. The results are hoped to give insights into the petrophysical behaviours of various lithologies, and provide theoretical and technical guidance for reservoir evaluation and prediction.

Near-bit apparent resistivity measurement method based on SPWM excitation

In order to improve the measurement accuracy of near-bit apparent resistivity and its measurement range, this paper excites the underground transmitting antenna by a sinusoidal pulse-width modulated (SPWM) current excitation method, which can improve the response of the receiving antenna and circuit in the resistivity measurement system under the usual square wave excitation, thus improving the measurement accuracy of near-bit apparent resistivity. In this paper, the effect of square wave, SPWM wave and sine wave excitation on resistivity measurement was studied, and the modulation algorithm and hardware control are programmed by DSP (Digital Signal Processor), and the SPWM signal is output by full-bridge inverter circuit and tuned antenna. The indoor experimental results show that the near-bit apparent resistivity measurement method based on the SPWM wave pulse excitation can achieve the measurement in the range of formation equivalent resistor value of less than 600kΩ. There is a high trend matching between near-bit apparent resistivity LWD curve and RT resistivity curve of well completion electrical logging in field tests of formation resistivity less than 2000Ω·m, which proves that the method can improve the accuracy of near-bit apparent resistivity measurement.

Typical misinterpretations and scientific concepts in well-logging geologic studies

The method and theoretical system of well logging geology have been widely used in the fields of basic geology, petroleum geology and engineering geology, but the different response sensitivity of different well logging series to geological information and the mismatching between geophysical properties of multiple well logs and geological genesis of rocks frequently result in misunderstandings in the research process of well logging geology. Therefore, it is in an urgent need to analyze the typical misunderstanding cases in the research of well logging geology and explore the corresponding scientific ideas and countermeasures. After analyzing the typical misunderstandings in the research of well logging geology, this paper investigates vertical resolution scale of various logging series and its contradiction with detection depth and illustrates the importance of the integration of different scales of data. In addition, the factor inducing “fake logging data” and its influence on interpretation evaluation are clarified and a set of ideas for well logging evaluation of geological interpretation is put forward. And the following research results are obtained. First, the typical misunderstandings in the research of well logging geology can be classified into two categories, namely geological body interpretation misunderstanding and reservoir property parameter calculation misunderstanding. Second, special geological phenomena, such as high-density and high-resistivity mudstone can lead to logging data ambiguity, so attention shall be paid to petrophysical response mechanisms during geological logging interpretation. Third, to carry out well logging evaluation of unconventional oil and gas, it is necessary to integrate new technologies of electric imaging logging, dipole acoustic logging and nuclear magnetic resonance logging, and the calibration of core data and the integration of geological ideas can improve the interpretation accuracy. Fourth, In the process of borehole structural logging analysis, sedimentary response, geostress evaluation and fracture identification, geological ideas shall be integrated to avoid the logging interpretation misunderstanding caused by the same response of different geological phenomena in well logs. In conclusion, the dialectical and systematic thinking from geology to logging and then to geology, from practice to recognition and then to practice and from “a narrow view” to “a broad view” can provide a scientific ideas for the comprehensive research of well logging geology.

Evaluation of irreducible water saturation by electrical imaging logging based on capillary pressure approximation theory

One of the most important metrics for evaluating oil and gas reservoirs is irreducible water saturation (Swir). The completion of oil and gas reservoir development tasks, such as fluid identification, productivity prediction, and water-flooded reservoir discrimination, requires the accurate evaluation of Swir. Nuclear magnetic resonance (NMR) logging can reflect the intricate pore structure of reservoirs, so it offers a natural advantage in the evaluation of Swir, but its high measurement cost leads to infrequent use. In geophysical logging, electrical imaging logging can obtain pore size distribution information at a lower cost. Hence, a method based on electrical imaging logging data is proposed to predict Swir. This method not only has a high degree of accuracy but is also cost-effective. First, the pore characteristics of the bound fluid were analyzed with the mercury injection capillary pressure curve. Based on the capillary pressure approximation theory, the reverse cumulative curve of the porosity spectrum was derived. And the physical meaning of its “inflection point” was clarified. Then, the resistivity of the formation containing just irreducible water was computed using the conversion between the core displacement pressure and resistivity. Finally, based on Archie's formula, the Swir at each depth of the reservoir was predicted. By using ultradeep carbonate reservoir logging data from the Yuanba gas field, the model was validated. The results demonstrated that the calculated values using this method agreed with the measured values from the cores. Compared with the core fitting method, the average absolute error is reduced by 2.61%, and the average relative error decreases by 12.0%. If NMR logging information is not present, this method serves as an effective supplement to accurately predict Swir.

The use of Electrical Resistivity Methods to Investigate Water Table Potentials of Awka South Local Government Area, Anambra State, Nigeria

Purpose: Geophysical exploration for water table characteristics were carried out in six (6) communities of Njikoka and environs through which water table depth, depth below the water table, thickness of the saturated zone, depth with reference to mean sea level (MSL) and types of aquifer were deduced. The proven geoelectric sections of the study area based on resisitivity from the subsurface and electrical log which confirmed that depth to water table of Njikoka and environs could range from 15 m – 100 m. Depth below the water table in the study area ranged 40 m (around Nimo, Enugu Agidi) to 200 m (Ifitedunu, Ukpo) while the thicknesses of the saturated zones (aquifers) varies from 25 m to 160 m within the respective communities. Depths to Mean Sea Level were delineated to range from – 20 m to – 198 m as obtained from the difference in the water table depths and the heights above sea level which is the elevations.
 Methodology: Subsurface geophysical exploration was employed in the research of groundwater availability of Njikoka and environs. Schlumberger Vertical Electrical Sounding which is the subsurface geophysical method was carried out only on two locations in each of the communities. The geophysical investigation was made with Earth Resistivity equipment
 Findings: From the revealed results the study area is dominated with low land topography and prominently composed of unconfined with less cases of confined aquifer as a result of the geological settings of the study area.

Study on stability of underlying room and pillar old goaf in close coal seam and mining of the upper coal seam

Possible issues during mining of the upper coal seam in old goaf of nearby coal seams, including step subsidence, gas overflow in goaf, and roadway around rock fragmentation. Using the Hanjiawa Coal Mine’s upper coal seam mining, which takes place 28 m above the working face of the lower coal seam, as the research’s focal point. The paper focuses on the self-stability of the coal pillar in the old goaf, the failure form of the upper coal seam mining floor, the roof caving rule of the old goaf in the lower coal seam mining of the upper coal seam, and the bearing capacity of the interlayer rock strata using the pillar goaf stability evaluation system, field geological borehole electrical logging and borehole peeping, finite element difference numerical calculation, and other methods. The conclusion that the old goaf’s coal pillar can be completely stable and that the interlayer rock strata can bear the stress of upper coal seam mining is reached. The results show that the failure depth of the coal pillar in the lower coal seam old goaf is 1–3 m, the maximum failure depth accounting for 15% of the width of the coal pillar, and the failure depth of the roof in the old goaf is 0–3 m; After the mining of the upper coal seam, the floor above the coal pillar of the lower coal seam is plastic failure, and the failure depth is 1–10 m, and the failure depth of the roof of the old goaf of the lower coal seam is 3–15 m, which is 4 times greater than that before the mining. The maximum failure depth of the interlayer rock strata is 22 m, accounting for 78.6% of the rock strata spacing. The interlayer rock strata can bear the mining disturbance of the upper coal seam. The plastic zone of the floor of the upper coal seam is not connected with the plastic zone of the roof of the lower coal seam.

Evaluation method for in-situ stress orientation using wave anisotropy and electrical imaging logging data: A case study from the Longmaxi Formation in Yongchuan area, Sichuan Basin

In-situ stress orientation is a key parameter in studying oil and gas migration and accumulation, analyzing the stability of borehole wall during drilling, carrying out horizontal well design, fracturing reconstruction and well pattern layout in water injection development. Accurately predicting the in-situ stress orientation of reservoirs is of utmost importance for oil and gas exploration and development. It is the most effective and commonly used method to evaluate the in-situ orientation by using the induced fracture and breakout fracture of imaging logging data. However, in cases where effective induced fracture or breakout fracture cannot be formed during drilling, the in-situ orientation cannot be evaluated by imaging data alone. Taking the shale reservoir of Longmaxi Formation in Yongchuan area as an example, this paper presents a novel method for evaluating in-situ orientation. Firstly, the in-situ orientation is determined relative to the core sample marker line through the wave velocity anisotropy experiment. Secondly, the core sample is rotated to obtain an unfolded image of the core surface. The orientation of the core marker line in the electrical imaging is then determined by comparing the core image with the electrical imaging logging image. By doing so, the true orientation of the core can be obtained. This method aligns well with the in-situ stress orientation determined through induced fracture evaluation, addressing the limitation of electrical imaging data in evaluating in-situ stress orientation in plastic strata.

КОМПЛЕМЕНТАРНОСТЬ МЕТОДОВ ИМПУЛЬСНОГО НЕЙТРОННОГО КАРОТАЖА И ЭЛЕКТРИЧЕСКОГО ДИВЕРГЕНТНОГО КАРОТАЖА В ОБСАЖЕННЫХ СКВАЖИНАХ

In production wells, nuclear-physical and electrical logging methods are used to study the backwater space. More well-known and widespread is pulsed neutron logging (PNL) [16] and its modifications. Electric divergent logging (EDC) is considered less common [2] in cased wells. Both methods solve the same problem, but they are still not ideal and have their drawbacks. This article presents the advantages and disadvantages of the PNL and EDC methods in comparison with each other. A significant criterion when choosing the preferred method for determining the current oil and gas saturation is the minimum error of the output results of the study by the method. The operating conditions of a particular deposit must be taken into account. When choosing the optimal method for determining the current oil and gas saturation from the point of view of the minimum error, the operating conditions of each specific field should be taken into account. The best results, however, will obviously be achieved by combining the above methods, which radically differ significantly both in their physical characteristics and in the principles of measuring nuclear physical and electrical parameter.

Evolution of electrical resistivity and NMR during early-stage maturation of an organic-rich chalk

This paper studies the changes in the electrical resistivity of an organic-rich source rock chalk containing a Type-IIs kerogen during early-stage maturation of the kerogen. As bitumen is generated during maturation, the chalk changes from water wet to a complex mixed-wet pore system, with the micritic pore space remaining water wet while the bitumen expelled into the macro pores converts some pores to oil wet. This mixed-wet system results in non-Archie electrical behavior with pronounced curvature of the I-Sw curve. We find that this curvature is well fit by connectivity theory. The connectivity theory parameters are determined both on native state core and from artificial laboratory pyrolysis which generates bitumen. NMR is used to distinguish the brine in micritic, water-wet pore spaces from that in the intergranular, mixed-wet pore spaces, from which the observed connectivity parameters may be independently estimated. Comparison between electrical resistivity and dielectric logs show that the connectivity parameters match the laboratory results over a calcareous section more than 300 m thick.

Summary of research methods for porosity and permeability of coalbed methane reservoir

In order to serve the research on the physical properties of coalbed methane reservoirs and improve the prediction effect of porosity and permeability of coal reservoirs, this paper, based on a large number of literature research, summarizes the concepts, influencing factors and prediction methods of coal seam porosity and permeability. The research shows that the main factors affecting the porosity of coalbed methane reservoir are coal petrographic composition, metamorphic degree, coal body structure and buried depth, compaction, tectonism, etc; The main influencing factors of permeability include component content, coal rank, coal body structure and in-situ stress, buried depth of coal seam, natural fracture of coal seam, matrix shrinkage, Klinkenberg effect, etc. The porosity prediction of coalbed methane reservoir generally adopts true and apparent relative density method, in addition, there are multiple regression method based on logging information, nuclear magnetic resonance logging method, etc; The measurement methods of CBM reservoir permeability mainly include the calculation method based on conventional logging, triaxial stress experimental research method, joint prediction method of nuclear magnetic resonance and electrical imaging logging, dynamic data analysis method and numerical simulation method. The development of coal seam porosity and permeability prediction technology needs innovative breakthroughs in hardware and software.

Stopkontak Pintar Berbasis Internet of things sebagai Solusi Manajemen Energi Listrik dengan Menggunakan Aplikasi Android

Leaving an electrical appliance connected to an outlet when not in use or on standby accounts for 80% of electricity wastage. A study conducted by the Lawrence National Laboratory, it was revealed that when a cellphone charger is still connected to a wall socket when not in use, there is still power being released. The purpose of this research is to make a smart socket based on the Internet of things (IoT) to be able to save electricity. An IoT smart socket that is designed to be integrated with an Android-based smartphone application. The IoT smart socket uses the ACS-712 current sensor and the ZMPT101B voltage sensor to measure electrical energy and then uses the Arduino Nano microcontroller and NodeMCU ESP8266 so that the socket can communicate with the Google Firebase cloud via Wi-Fi connection to the internet. The IoT smart socket uses a relay module as a switch, and the micro SD and RTC DS3231 modules record and store data (data logging) of electrical energy information that has been issued. The IoT smart outlet is integrated with Android smartphone applications created through Android Studio. The IoT smart socket in this study has 2 socket holes and features Wi-Fi pairing, electrical energy measurement, data logging, and socket scheduling (timer). The IoT smart outlet has an average measurement error of 3.27% when compared to a measuring instrument, and there is an error in the outlet timer feature with a delay of 5 to 30 seconds. The IoT smart socket is still said to be valid and can function properly.

Delineation of horizons and suites based on quantitative indicators of oil-field geophysical parameters

The limits of horizons IX and X and a parting suit in the productive strata are adjusted using the methods of electrical resistivity of clay and the maximal potential of sandy rocks as a case-study of Gunsehli and Bahar fields in the South-Caspian Basin. It is known that in oil-field geophysics, delineation of oil and gas bearing suites and horizons by the existing methodology uses the curves of standard electric logging. However, despite that the standard electric logging reflects apparent resistivities of all rocks across the section, it disalllows evaluating stratigraphic characteristics of rocks. Differentiation ability of the electric logging curves depends on many factors, including variation of borehole diameter, thickness and resistivity of surrounding layers, drilling mud resistivity, equipment parameters, etc. All these have their negative impact while outlining the oil and gas bearing suites and horizons using the standard electric logging. In this respect, in distinction from the existing methodology, this article suggests to correlate borehole logs using not the apparent resistivity curves but the curve of the true resistivity variation in clays with depth and the change in maximal self-potential in sandy layers. It is shown that adjsutment of outlines of lithostratigraphic units, including horizons and suites, and correlation of well sections based on the new approach applied jointly with other data for identification of oil and gas pools opens up new opportunities, which, in turn, can enhance geological efficiency of well logging.

SVR-based weighted processing method for electrical imaging logging in oil-based mud

Electrical imaging logging in high-resistivity oil-based mud (OBM) has been one of the hotspots in petroleum exploration and development recently. Compared with the traditional electrical imaging logging in water-based mud (WBM), the core issue restricting the application of electrical imaging logging in OBM is that the mud-layer with high impedance prevents the emitted current from flowing into the formation and seriously disturbs the measurement of formation properties. Here, a SVR (support vector machine regression)-based weighted processing method is proposed to resolve the intractable problem and three key parameters are obtained simultaneously. First, the equivalent circuit model of electrical imaging logging in OBM is established and the drawback especially occurring in low-resistivity formation is analyzed. Then, a weighted coefficient applied to the mud-layer impedance is introduced for the quantitative calculation of formation resistivity, and the change of relative formation permittivity and mud-layer thickness can also be depicted with weighted processing. Next, a SVR model is established to inverse the weighted coefficient and then figure out the inversed parameters including the formation resistivity, the relative formation permittivity, and the mud-layer thickness. A stochastic parameter model is adopted to verify the validity of SVR model. Finally, two deviated formation models further test the advantage and robustness of SVR model. The results demonstrate that the SVR-based weighted processing method possesses a terrific performance and all the three parameters can be calculated simultaneously regardless of the borehole wall condition. This study will provide a new approach to the data processing and interpretation of electrical imaging logging in OBM.

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.

Reservoir characterization of Maracangalha sandstone using measurements on outcrops and well logs

In this research, we performed petrophysical measurements using conventional techniques (Pycnometer and gas permeameter), resistivity and chargeability electrical, besides nuclear magnetic resonance (NMR), on 122 shale sandstone samples collected from outcrops of the Maracangalha Formation in Frades Island, Bahia Brazil. This Formation is an of the main hydrocarbon reservoirs in the Recôncavo Basin in Brazil, but little petrophysical information is available. Electrical measurements were performed using a sample holder build with four-electrode, two for current injection and two for electrical potential measurements, where the rock samples were inserted under condition 100% saturated with multiples salinity solutions. NMR measurements were also obtained with saturated samples and under the condition of partial saturation. The conventional, electrical, and NMR data were analyzed together, resulting in important petrophysical parameters for the lithological characterization of the Maracangalha Formation sandstones. These samples were characterized according to your effective porosity, cementation exponent, volumetric-solid conductivity, clay content, mean grain, and pore-throat sizes. Such laboratory results allowed developing an integrated approach to interpret geophysical well logs of the Maracangalha reservoir. These logs, including gamma-ray, porosity (density, sonic and neutron) and electrical data, were interpreted in terms of shaliness, effective porosity, and partial water saturation, supported by our experimental petrophysical results. In particular, to complete this interpretation was used a combination of electric logs was used to describe the true resistivity at the invaded and in the virgin zone of this reservoir. Taking into account the effects of weathering in the samples used, these results contributed to the formation of a petrophysical database for the Maracangalha Formation, as well as its use as guide values for new interpretations in geophysical profiles in this region.