Reservoir Units Research Articles

High-resolution impedance estimation using refraction and reflection FWI constraints: the Fortuna region, offshore Equatorial Guinea

Seismic imaging and reservoir characterization in the Fortuna region, offshore Equatorial Guinea, is beset with various geophysical challenges related to the presence of extensive, but small-scale low-velocity gas pockets, which give rise to significant and cumulative image distortion at target level. This distortion had not been resolved in a vintage 2013 broadband pre-stack depth migration project, as the velocity model was not sufficiently well resolved, but was subsequently addressed successfully in a project conducted using high-resolution non-parametric tomography with improved broadband deghosted data. The primary objective of that subsequent project was to improve the understanding of the internal structure of the Viscata and Fortuna reservoirs, and this objective was met via clearer internal imaging of these reservoir intervals and the overlying gas-charged sediments. The follow-on work considered here deals with the use of full waveform inversion to further delineate small-scale velocity anomalies associated with the highly compartmentalized reservoir units, and also to use the full waveform inversion velocity model as a constraint during acoustic impedance inversion. We compare the results of impedance inversion using both a conventional approach (with the well-log velocities to build the background trend), with a new approach using a trend derived from high-resolution waveform inversion velocities.

Impact of rift dynamics on palaeoenvironmental conditions and hydrocarbon system development (northern Upper Rhine Graben, SW Germany)

The Upper Rhine Graben (URG), a classical hydrocarbon (HC) province, is part of the European Cenozoic Rift System. The rift graben development has led to a complex basin fill of terrestrial and marine Cenozoic deposits, providing several HC source and reservoir units. The aim of this study is the multidisciplinary analysis of the palaeoenvironmental conditions and source-rock development within the transgressive marine intervals, and the palaeothermal history of the graben system to improve the understanding of the HC system development. Palaeoenvironmental conditions are strongly influenced by rift-related tectonic activity. Transgressive marine intervals in times of major subsidence show high terrestrial input from the graben shoulders, leading to mainly terrigenous gas-prone kerogen, while transgressive marine intervals during weak tectonic activity are dominated by marine–brackish palaeoenvironments and oil-prone kerogen. This differs clearly from the previously suggested HC potential of these intervals. Thermal maturation analysis shows nearly constant maturation with depth, which is atypical for burial-controlled maturation. It indicates significant secondary thermal overprinting related to long-lasting very hot hydrothermal fluid systems, concentrated along fault zones. Therefore the development of the depositional setting, kerogen composition, thermal maturation and the HC potential is directly linked to the dynamics of the rift system development. Supplementary material: detailed results of all three wells are available at https://doi.org/10.6084/m9.figshare.c.4183106

Gunung Gare Kota Pagar Alam Dengan Konsep Zero Runoff System

Internal runoff is caused conversion of green land into be constructed where if there is rain with high rainfall intensity then rainfall runoff will become large and trigger water puddle (overflow) because of reduced area to absorb water. Zero runoff rainwater needs to be applied to the building and land use where the runoff volume (input) can be withstand up to 100% and runoff flow volume (outflow) of 0% or maximum of 3% so that it can reduce the impact of decreasing peak floods (water puddle) the purpose is to analyze the runoff of rain water from the roof of building so it can be useful for processing and utilization of rain water and analyze the needs of absorption wells, reservoir and maximum discharge to retention pond. Roof of parcel area of 13.438,24 m2 is 0,88336 m3/s the need of absorption wells in building is as much as 8 units of recharge wells with Ø 100 cm.reservoir that is needed in the building is 45 units of reservoir with size 30m3. The volume of retention ponds to accommodate runoff discharge from the land use area of 273.339,4 m2 and the roof ot the building area of 13.438,24 m2 is equal to 12.259,4 m3/year at Gunung Gare office complex of Pagar Alam city.

Geological controls on the heterogeneous hydrocarbon compositions of the biodegraded Grosmont Formation bitumen, Western Canada Sedimentary Basin

The hydrocarbon composition of the Grosmont Formation bitumen was investigated in 51 core samples by gas chromatography–mass spectrometry (GC–MS). The bitumen composition is highly variable and is heavily to severely biodegraded. Molecular ratios based on biodegradation-resistant compounds are highly uniform laterally and vertically, even across shale barriers indicating the bitumens are genetically related. Biodegradation-resistant biomarker maturity parameters suggests the bitumen was likely sourced during the early oil window stage of petroleum generation. Biomarkers responding to biodegradation display strong lateral and vertical variations in composition with geochemical profiles based on concentration data, displaying dramatic offsets when shales are present indicating the reservoir units are compartmentalised. Considering the relationship between 25-norhopanes and hopanes, the hydrocarbon composition data indicate progressive hopane degradation, both with concomitant formation of 25-norhopanes and hopane degradation without the formation of 25-norhopanes. In wells 07-08-085-18W4 and 10-12-093-24W4, the degradation of hopanes occurs in Upper Grosmont unit 3 (UG3) without the formation of 25-norhopanes (unless 25-norhopanes have been synchronously consumed), whereas in unit UG2, hopane degradation occurs with the concomitant formation of the 25-norhopanes. Therefore, the shale compartmentalizes the reservoir creating two isolated environments whereby the biogeochemical setting contributing to 25-norhopane formation is found in the UG2 unit, whereas it is absent or inactive in unit UG3. The degradation of the 22R epimer prior to the 22S epimer in the C31–C33 17α-hopanes was recognized in well 16-05-088-19W4, which indicates that the consortia of microbes more readily biodegraded the epimer having the biological conformation.

Efficiency Analysis of Processing Injection Wells with Acid Compositions

Efficient development of oil reservoirs includes measures to restore and enhance the porosity and permeability properties of reservoir units that are gradually impaired during well operation. As a rule, various technologies of bottom-hole formation zone processing (BZP) of wells are used for these purposes. Special requirements to BZP technologies are applied during interventions in low-permeability reservoirs where the geological structure of reservoir units has the highest impact on the efficiency of works. In this relation, it seems interesting to study the specifics of geological structure of reservoir units in a laboratory for the efficiency of interventions using physical and chemical methods of reservoir stimulation. The research objective is to assess the efficiency of processing reservoir units with acid compositions of various concentration and type. Using laboratory experiments, physical and chemical parameters were quantitatively assessed that characterize the speed and depth of interaction between acid compositions and reservoir units.

Petrophysical properties of the reservoir unit (1C) for Upper Shale Member from Zubair formation in Luhais field

The research dealt with the reservoir division for Upper Shale Member from Zubair formation in Luhais field, Where it was divided into six units of reservoir and non-reservoir, including the main reservoir unit 1C, which is the subject of research in this study, and studied in terms of thickness and lithology. The reservoir unit 1C was associated with environmental sediment, which was the environment of the tidal channels, explaining the sedimentation mechanism that helped to form the oil traps and improve the petrophysical characteristics. The log interpretation was used to determine and calculate the petrophysical characteristics of reservoir unit 1C. The total and effective porosity ratio was calculated with the highest and lowest value, and its porosity was represented by a three-dimensional model representing its distribution in the field, In addition, permeability was calculated through the relationship between porosity and permeability from the pulp where the permeability equation was extracted from the best straight line values containing an unknown value, By compensating for the porosity value of the logs, the permeability could be calculated for the depths of wells that do not contain a core. The permeability of unit 1C is represented by three-dimensional models that are distributed across the field. The oil and water determinations of unit 1C were studied and their existence periods were determined for all wells of the field. The work of three-dimensional models and longitudinal and transverse sections represented the distribution of oil and water polysaccharides in unit 1C. The level of contact of oil - water was determined at a depth of 2753 meters.

Refinement of the Geologic Structure of the Ozernoye Field for Improving the Development Efficiency

The Ozernoye field is a unique geological object. The primary geological and geophysical materials obtained during its inspection allow coming close to developing universal methods for carbon-containing field logging, which can be extended to other geological objects. The research objective is to forecast the development of reservoir units in undeveloped parts, determine the expected parameters of their class, the maximum total net reservoirs and the number of sandy formations, carry out their indexation and detailed paleogeographic reconstructions of the inspected area. Using the paleogeographic methods, retrospective reconstructions of sedimentation accumulations were performed. The facies analysis of sediments made it possible to elucidate the reservoir unit genesis.

Evaluation of the Influence of the Facies Genesis of the Reservoir Unit of the Fainsk Oil Field YUS<sub>1</sub> Facility on the Effectiveness of Integrated Processing of the Injection Wells Bottomhole Formation Zone with the Application of Acid Compositions

One of the main problems with the bottomhole formation zone processing is the choice of an acid composition adapted to the peculiarities of the geological structure of the facility. The highest technological effect of the geological and technical interventions using physicochemical formation stimulation techniques is achieved when the genesis of processed deposits is taken into account during the process of treatment planning. The research objective is to assess the impact of the reservoir units formation (genesis) characteristics on the effectiveness of integrated processing of the bottomhole formation zone of injection wells with the application of acid compositions. Using the geological and routine analysis of the development process parameters for deposits located in various facies zones, the operational benefits of the bottomhole formation zone integrated treatments in injection wells were evaluated and practical recommendations were provided.

Determination of flow units of Yamama Formation in the West Qurna oil field, Southern Iraq

The major objective of this paper is to recognize the flow units of Yamama Formation in the west Qurna oil field, south of Iraq. To attain this objective, four wells namely, WQ-23, WQ-148, WQ-60, and WQ-203 are selected and analyzed. The two techniques hat proposed by some scientists to identify flow units are tested and verified. Results are also enhanced using well logs interpretation and the flow areas are proposed through the studying of the behavior of different well logs. Results of applying the two proposed techniques identify six flow reservoir units for the wells WQ-23, WQ-148, WQ-60, and WQ-203, respectively. This study also shows that the flow reservoir properties in the Yamama Formation improved towards the northeast of the West Qurna oil field.

Genetic Zoning of the YUV<sub>1</sub> Productive Horizon Deposits within the Tagrinsko-Yarainersky Bar

The developed litho-sedimentological model of deposits of the YUV1productive horizon makes it possible to choose the most effective technique for supplementary exploration of a natural reservoir and improve the quality of geological justification for its subsequent development. The research objective is to carry out paleogeographic and paleostructural reconstructions, to identify facies complexes in the Upper Jurassic productive deposits, and to identify zones for the development of improved reservoir units. With the help of paleogeographic and facies methods, the geological regularities of the development of the territory encompassing the Tagrinsko-Yarainersky Bar in the Late Callovian-Oxfordian Stage were studied.

Studies on Applying Acid Compositions to Treat the Western Siberian Field Bottomhole Formation Zone

Effective development of oil deposits includes the measures to restore and improve the porosity and permeability properties (PPP) of reservoir units, which inevitably deteriorate during the operation of the field. For this purpose, various technologies of bottomhole formation zone acid treatment (BFZAT) are used. These approaches are sufficiently developed and usually do not require additional laboratory adaptation. Specific requirements for technologies that include acid effect on the formation are required for interventions on low-permeability reservoirs (LPR), where the influence of the mineralogical composition of rocks and their porosity and permeability properties on the efficiency of BFZAT is the most significant. Therefore, during interventions development for LPR using acid methods, it is necessary to correctly assess the capabilities of a particular method (composition) in relation to specific conditions. This can be achieved by conducting standard laboratory tests (determination of rock carbonation and mass loss in 12% hydrochloric acid) and additional experiments to determine the mass of the secondary sediment, as well as the optimum reaction time at the formation temperature. The research objective is a laboratory research on the selection of acid compositions for bottomhole formation zone treatment for a number of low-permeability reservoirs in Western Siberia. Standard and special laboratory studies have allowed suggesting the most optimum acid compositions adapted to “rigid” formation conditions.

Application of Lithofacies Modeling for Evaluating the Effectiveness of Enhanced Oil Recovery in the Fainsk Oil Field

A lithofacies model of the Fainsk oil field YUS11 formation was built. The results of interventions for oil production stimulation and enhanced oil recovery depending on the section penetrated by wells were considered. Criteria for selection of various types of interventions in particular geophysical conditions were given, and recommendations on the selection of technologies for bottomhole zone processing (BZP) and enhanced oil recovery (EOR) were made. The research objective is to evaluate the effectiveness of interventions in terms of enhanced oil recovery, adapted to the specific features of the field geologic structure aspects. Through the use of sedimentary deposits facies analysis method, a lithofacies model of the Fainsk oil field YUS11 formation was constructed. The application of field-geologic analysis gave an option to evaluate the technological effectiveness of interventions for oil production stimulation and enhanced oil recovery depending on the reservoir units genesis penetrated by wells.

Using Borehole Seismic Data in Designing of Development and Further Exploration of Oil Fields

Borehole seismology allows studying the specific features of the geological structure and physical properties of deposits in the borehole environment using waves of various kinds based on the analysis of characteristics of these waves, their rates propagation, attenuation, space polarization, and the nature of rock anisotropy. The research is intended to study the wave fields of various types of waves taking into account their dynamic, speed and polarization characteristics and the features of geological structure both in the vicinity to the borehole and laterally in the crosshole space. Using the borehole seismology method, the geological structure of reservoirs was specified; a prediction was given as to the development of enhanced reservoir units in the crosshole space.

Diagnostics of Facial Complexes in Bajocian-Bathonian Deposits of the Peschanoye Field

The establishment of the paleofacial nature of sand bodies is of an utmost importance in the search for lithological traps of oil and gas, and also allows forecasting their spatial location, the position of wedging zones and changes in the reservoir properties of reservoir units. The research objective is to determine the genesis of productive deposits of the Bajocian-Bathonian age and to reveal the features of their geological structure. With the help of facial and electrometric methods of research, facies complexes were identified in deposits of the Bajocian-Bathonian age.

Assessment of Radial Drilling Feasibility at the Fields of the Orenburg Region

The development and use of the radial drilling technology has been a controversial issue in the oil and gas industry for a long time. Nowadays, almost all big oil and gas producers deal with the question of its practical use at particular fields. The results of works carried out at carbonate reservoir units of the Orenburg Region were analyzed in the article. The ways to improve the existing technology of radial drilling were also offered. The research objective is to evaluate the technological efficiency of radial drilling application at the fields of the Volga-Ural oil and gas region with carbonate reservoir units. The results of radial drilling were characterized with the help of the detailed geological and field analysis and their quantitative evaluation was given.

Geological modeling using Petrel Software for Mishrif Formation in Noor Oil Field, Southeastern Iraq

Petrel is regards one of the most important software to delineate subsurface Petrophysical properties to the reservoir. In this study, 3D Integrated geological models has been built by using Petrel software. The process includes integrated Petrophysical properties and environmental approaches. Noor oil field within Mishrif Formation in terms of structural geology represents asymmetrical anticlinal fold with direction NW-SE. Porosity and water saturation model have been built. The reservoir was divided into several reservoirs and Non-reservoir units depends on the Petrophysical properties for each zone. In addition, intact model for the reservoir in terms of porosity and water saturation have been built. MB reservoir unit represents the most important oil bearing unit according to the high porosity and low water saturation are present in this unit. MB reservoir unit in terms of Paleoenvironment which represent the shoal including rudist biostrome. Rudist biostrome buildups comprise the major oil producing reservoirs in the carbonate strata during Cretaceous Period.

Using Multiattribute Analysis to Predicting Effective Porosity of Yamama Formation in Nasriya Oilfield Southern Iraq

Emerge application was used in Hampsson-Russell programs and that uses a combination of multiple 3D or 2D seismic attributes to predict some reservoir parameter of interest. In this research used the seismic inversion technique was performed on post-stack three dimensions (3D) seismic data in Nasriya oilfield with five wells and then used this results in Emerge analysis (training and application) were used to estimate reservoir properties (effective porosity) with multiattribute analysis derive relations between them at well locations. The horizon time slice of reservoir units of (Yb1, Yb3 and Yc) of Yamama Formation was made for property (effective porosity) to confirm match results and enhancement trends within these units. Because of the good prospects of the oil in the rocks of Cretaceous generally and Yamama Formation specially in the Nasriya oilfield and in view of the economic importance of Yamama Formation, which is considered as important formation that contains hydrocarbon accumulation, and one of the most important and oil production reservoirs in southern Iraq.

Characterizing the Middle–Upper Miocene Reservoir Intervals of a Producing Field in the Niger Delta Basin: An Application of Facies, Sequence Stratigraphic and Petrophysical Analyses

Well log and core data were used to carry out detailed facies, sequence stratigraphic, and petrophysical analyses of the “Iota field” in the onshore Niger Delta Basin. The aim was to recognize facies distribution, environments of deposition, stratigraphic framework, reservoir continuity, and property distribution for better understanding of reservoir characteristics across the field. Sedimentological evidence reveals the occurrence of fifteen lithofacies, which were further classified into eight facies associations. The facies associations depict deposition in the offshore, offshore transition, lower shoreface, upper shoreface, estuarine channel, tidal channel, and fluvial channel environments. Sequence stratigraphic analysis reveals the occurrence of three maximum flooding surfaces and three sequence boundaries, which reflect series of transgressive and regressive episodes during the Serravallian–Tortonian age. Two depositional sequences comprising lowstand system tract, transgressive system tract, and highstand system tract packages were recognized. The sand and shale of the fluvial, tidal, estuarine, shoreface and offshore deposits, constitute the reservoir and seal/source rock packages. Correlation indicates that the reservoir packages have good lateral continuity, except where channel incision has occurred. Petrophysical analysis shows that the reservoir units have fair-to-good porosity and good- to-excellent net-to-gross qualities. Dominance of oil-bearing zones were detected at shallow to deeper interval at the northern section of the study area, with few gas-bearing intervals occurring at the intermediate intervals of the southern section. Overall, integrated analytical approach has provided more insight into the facies and reservoir quality distribution, thus reducing subsurface reservoir uncertainties.

Impact of structural setting on hydrocarbon trapping mechanism of onshore Niger Delta basin, Nigeria, using seismic attribute analysis

The evaluation of hydrocarbon trapping system in an onshore Niger Delta basin, Nigeria was studied using well log and seismic data. This is very important in estimation of production cost and assessment of viable reservoir units in petroleum industry. It is the main aim in reservoir characterization, in order to estimate the geometry and trapping mechanism of any particular field under investigation. These were achieved through the integration of 3D seismic and well log data that was acquired from an Onshore Niger Delta basin, Nigeria. From the well logs, three reservoir units was identified namely RS1, RS2, RS3 and these were mapped based on the curve signatures of the geophysical logs. These identified hydrocarbon bearing intervals were mapped on the seismic section using checkshot dataset for time to depth conversion. Four horizons and a total of thirteen fault traces were mapped within the region, with two characterized building structural faults of F2 and F3 features. Fault F4 and F7 are antithetic fault that trends north east to south west and the trapping mechanisms for the region are both a four way closure and fault assisted closure, as the trap is an up dip fault closure against the up thrown side of fault F8. Amplitude, variance and coherence attributes shows the faulting structure of hydrocarbon migration channels and path ways, through which hydrocarbon migration and accumulation occurs within the region. A significant level of contribution was achieved with the variance attributes showing a better resolution of an instant fault detection or identification compared to other attributes studied within the field of interest. The identified hydrocarbon bearing units lies within the same depth across the entire wells. This proved that the region has exhibits little or no tectonic deformation. The presence of structural features such as antithetic and synthetic is responsible for the hydrocarbon entrapment within the region. A detailed analysis of the study location revealed highly faulted region that exhibits a typical Niger Delta tectonic settings.

Pore-throat characteristics of tight sandstone reservoirs composed of gravity flow sediments: Yingcheng Formation, Longfengshan sag, China

The Lower Cretaceous Yingcheng Formation in the Longfengshan sag (Songliao Basin, China) represents a typical tight sandstone reservoir that hosts large accumulations of hydrocarbons. The lacustrine sandstones mainly reflect gravity flow deposits making up various lithofacies displaying varying degrees of heterogeneity. This study reports on the links among gravity flow type, diagenetic overprinting and pore-throat characteristics that control reservoir quality. Core observations, especially grain size variations and related sedimentary structures are used to differentiate types of gravity flows. Microscopic observations, cathodoluminescence, scanning electron microscopy, pressure-controlled mercury injection tests and rate-controlled mercury injection tests are used to determine the mineralogy, sedimentary composition and pore-throat characteristics of the tight sandstones.In the study area, the gravity flows are divided into muddy debris flows, sandy debris flows, high-density turbidity flows, low-density turbidity flows and mud density flows. The petrophysical properties of these different gravity flow sediments reflect a range of permeability and porosity characteristics. Because of their mud-dominated textures and related weak compressive strength, mud density flows and muddy debris flows become ineffective as reservoirs during burial. In contrast, for approximately similar burial depths, turbidites and sandy debris flows show better reservoir quality. However, reservoir units with high porosities still possess considerable heterogeneity; this is especially true of some sandy debris flows that possess large amounts of secondary pores but which are not charged with hydrocarbons. In particular, in some poorly sorted sandy debris flows that are characterized by high contents of fine-grained matrix, some of the pore throats are blocked by matrix material. Moreover, the dissolution of feldspars and volcanic debris led to the formation of authigenic clays and quartz, which preferentially developed in pore throats with small radii. This process significantly reduced permeability.Overall, the permeabilities of the sandy debris flows are generally lower than those of the turbidites. Due to their relatively large-radius pore throats, turbidites can be categorized as potential effective hydrocarbon reservoirs in the study area. This research provides significant insights into the characteristics of pore throats within tight reservoirs consisting of gravity flow sediments in lacustrine basinal settings.