Thin Reservoir Research Articles

Application of model-based acoustic impedance inversion in the prediction of thin interbedded coal seams: a case study in the Yuwang colliery, Yunnan Province

The Permian coal seams in eastern Yunnan and western Guizhou are thin, numerous, and staggered with other thin coal seams. Depicting the fine characteristics of coal reservoirs is pivotal for the safe and efficient exploitation of coal and coalbed methane (CBM), and is important for transparent mining. To improve the inverse resolution and accuracy of predicting reservoir thickness, this study used the model-based acoustic impedance (AI) inversion method that utilizes seismic and logging data. This method changes seismic data, reflecting stratigraphic interfaces, into AI data, reflecting lithologic structures. Moreover, it avoids the relevant assumptions of wavelets and reflection coefficients. Compared with other inversion methods, model-based AI inversion strengthens the description of thin reservoir horizontal and vertical changes. The results showed that comprehensively using intermediate-frequency seismic information and high-low-frequency logging data greatly broadens the seismic data frequency band and improves the dominant frequency of the reflected wave. Furthermore, the AI profile resolution and the prediction accuracy of the physical parameters for the target geological body can be improved. A cross-validation comparing the inverted thickness and measured thickness of borehole cores was applied to achieve fine prediction (error of appropriately 0.02–0.4 m), providing a basis for CBM development.

Case Study: Oil Production Optimized With Autonomous Inflow Control Devices Offshore Malaysia

_ Advanced well completions have proven to be an effective method of moderating gas breakthrough while producing a thin oil rim when placed in a heterogenous, carbonate reservoir. In addition, several studies have proven that the application of autonomous inflow control devices (AICDs) acts as a type of insurance policy against geological and dynamic reservoir uncertainties to reduce the risk and variation in the expected oil production profiles. During 2019 and 2020, Sarawak Shell Berhad conducted development campaigns in the central Luconia province in a thin oil rim carbonate reservoir offshore Sarawak, Malaysia. The horizontal, approximately 6,000-ft development wells were expected to intersect with different geological layers with varying rock properties, resulting in an uneven reservoir influx toward the wellbore. Oil production from these wells was expected to suffer severely from early gas and water breakthrough. To produce the oil rim without the risk of early gas production, global production optimization specialist, Tendeka, incorporated FloSure AICDs in the lower completion design at the reservoir interface along the horizontal section of the wells. As an active flow control device, the technology delivers a variable flow restriction in response to the properties of the fluid entering the wellbore and the rate of flow passing through it to help manage gas coning/cusping risks. The fluid is then lifted to surface with natural in-situ gas lift built into the upper completion. A three-phase development was planned for the field, and to date, two phases have been completed. New-Generation ICD The first AICD completion was installed in Norway in 2008 and widely implemented in the Troll field in 2013 with very encouraging results (SPE 159634). However, its use is relatively new to both the Asia Pacific region and this type of application. Similar to a standard ICD which balances the influx of reservoir fluids, the FloSure AICD will delay the production of unwanted effluents prior to their breakthrough (proactive solution). However, once a breakthrough occurs, the device restricts the production of unwanted effluents with lower viscosity, such as gas (in light oil applications) and both gas and water in viscous oil production (reactive solution) (OTC 30403, OTC 30363, SPE 193718). The device delivers a variable flow restriction in response to the properties of the fluid and the rate of flow passing through it. Flow enters the device through the nozzle in the top plate of the body. This impacts the disk and spreads radially through the gap between the disk and the top plate, then turns around the top plate and is discharged through several outlet ports in the body (Fig. 1). The overall geometry of the device is critical to its ability to balance these forces effectively and create the desired fluid-dependent pressure drop. Field A employed 7.5-mm AICD valves to match the performance of the devices to the potential well flow rate. The oil, water, and gas viscosities are 0.40 cP, 0.27 cP, and 0.018 cP, respectively, at downhole flow conditions.

Diagenesis of continental tight sandstone and its control on reservoir quality: A case study of the Quan 3 member of the cretaceous Quantou Formation, Fuxin uplift, Songliao Basin

Research on the diagenesis of continental sandstone reservoirs can provide scientific guidance for the prediction of reservoir sweet spots. The low permeable-interbedded thin and thick sandstone reservoirs of the Cretaceous Quantou Formation's Quan 3 Member in the Fuxin Uplift, Songliao Basin, were used as an example in this work to investigate the diagenesis of continental tight sandstone and its influence on reservoir quality. A large number of thin section, scanning electron microscopy, granularity, X-ray diffraction, and petrophysical property measurements were used to study the petrological characteristics and diagenesis. The reservoir space evolution mode of continental sandstones in this area was constructed by combining diagenesis sequences and the evolution of petrophysical properties of the Quan 3 Member. The results show that the compositional maturity of the sandstone reservoirs of the Quan 3 Member is relatively low and their lithologies are mainly lithic feldspar sandstone and feldspar lithic sandstone, followed by lithic arkose sandstone, feldspathic litharenite and a small amount of lithic sandstone. The average particle size of the target sandstones is 0.11 mm, and the fine sandstone to coarse siltstone are favorable reservoirs. The studied sandstone reservoirs have undergone intense diagenetic transformations, including compaction (pressure solution), cementation, dissolution, and metasomatism. Moreover, the complex diagenetic environment changes in the Quan 3 Member include early alkaline-acidic→mid-alkaline→late acidic. The shallow sandstones are in the meso-diagenetic A1 stage; when the burial depth exceeds 800 m, they enter the meso-diagenetic A2 stage; and when the burial depth exceeds 1600 m, they enter the meso-diagenetic B stage. It was found that diagenesis has significant control over the quality of continental sandstone reservoirs. Compaction is the primary factor controlling the quality of the target reservoir. It controls the differences in the petrophysical properties of the reservoirs in the eastern and western regions; that is, the physical properties of the Quan 3 Member in the east are higher than those in the west. Cementation and dissolution are secondary controlling factors of reservoir quality that control the differences in reservoir petrophysical properties in the northern and southern regions; that is, the physical properties of the Quan 3 Member in the north are better than those in the south. The most favorable reservoirs of the Quan 3 Member are developed in the Fuyu Oilfield, which is distributed in the southeast region and develops fine sandstones of branch channels and meandering river point sand bars of delta plains that suffer the least compaction and the strongest dissolution. This study may provide crucial clues for predicting the sweet spot reservoirs of the Quan 3 Member in the study area. Furthermore, the study provides a reference for the different diagenesis controls on the pore space evolution of continental tight sandstone reservoirs.

Study on Theoretical Model and Influencing Factors of High Propagation of Vertical Well Pressure Fractures in Block S

The gas reservoir in block S is relatively thin, and the fracture height of the thin reservoir is out of control seriously, and the effective support efficiency in the fracture is less than 50%. In view of this problem, this paper investigates the application status of fracture control and high-pressure fracturing technology, and carries out the research on the theoretical model and influencing factors of high expansion of vertical well pressure fractures in block s. The research results show that the in-situ stress difference between reservoirs is the most critical factor to control the fracture height, which directly determines the success rate of fracturing construction. When the in-situ stress difference between reservoirs is greater than 4MPa, the fracture height can be effectively controlled. According to the in-situ stress profile and geological data of drilled wells in block s, it is suggested to select the interlayer reservoir with in-situ stress difference greater than 4MPa and low elastic modulus for fracturing construction.

AVO Detuning Effect Analysis Based on Sparse Inversion

The wave field characteristics of thin reservoirs are extremely complex due to the tuning and interference between the top and bottom interfaces of the reservoirs, which leads to large uncertainty in thin layer AVO (Amplitude Versus Offset) analysis. In order to reduce the uncertainty of thin layer AVO analysis, we study the uncertainty dominant factors of the effect of thin layer on the AVO response characteristics from the aspects of theoretical derivation and forward simulation. Based on the research results, we use the AVO fitting forward method with offset and tuning utility as the joint inversion operator to establish an AVO detuning effect method, based on the sparse fitting inversion strategy, and study the objective function of the fitting inversion method. We optimize the sparsity constraints and the sparsity method to reduce the non-independence of multiparameter variables and seismic data, and the noise of inversion. Through the verification analysis of the model using actual data, the AVO detuning effect method studied in this paper has a correct and reasonable technical theory and obvious application effect.

3D experimental research of innovative VH-SAGD to enhance recovery of thin layer oil sand reservoirs

In thin layer oil sand reservoirs, the vertical and horizontal combined wells steam assisted gravity drainage (VH-SAGD) can avoid validly the problems of low steam efficiency and the high heat loss induced by the traditional SAGD technology. However, there are few laboratory studies about steam chamber development and production performance on the VH-SAGD. To fill this gap, a 3D large-scale physical model with temperature sensors was designed based on the similarity criterion, the experiment was carried out to simulate the production process of VH-SAGD. Then the development characteristic of steam chamber was captured by monitoring the temperature distribution changes. Finally, the production performance at each steam chamber development stage was analyzed. The experimental results showed the steam chamber development experienced the formation stage, the longitudinal development stage, the lateral expansion stage and the stabilization stage. The formation of triangular cold oil area indicated the steam chamber is mature, and the appearance of smooth steam front funnel indicated the steam chamber stopped developing. This research revealed the steam chamber development characteristics and the production performance of VH-SAGD, which can provide a reference value for optimizing injection and production parameters and predicting recovery factor for VH-SAGD in thin layer oil sand reservoirs.

Impact of model and data resolutions in 4D seismic data assimilation applied to an offshore reservoir in Brazil

Data assimilation is the process where reservoir models are calibrated using dynamic data. The goal is to reduce uncertainties related to reservoir properties for more assertive model-based forecasts and decisions. The use of 4D seismic data as input to this process allows model properties to be updated so that dynamic changes are better represented in the entirety of the reservoir. However, in many cases, the higher the number of grid blocks, the more time consuming are the models' simulation. Thus, the balance between the fidelity of models and simulation runtime in a project is crucial in the planning of activities. The objective of this work is to discuss the impact of using grids with different resolutions and explore options to incorporate 4D seismic maps in data assimilation and production forecast. Through a real field application, we evaluate the use of two grids with different vertical and lateral resolutions, using the Ensemble Smoother with Multiple Data Assimilation (ES-MDA) method. The available high-quality seismic data, applied to a Bayesian inversion, generated 4D impedances that helped identify important dynamic changes that happen at intermediate layers of a thin reservoir (averaged 25 m thickness), located in Brazil. Thus, we also evaluate two approaches for models updating with 4D seismic data: treating the entire reservoir as a single interval, and considering a greater vertical resolution by adding information at intermediate layers. Overall, well production misfits between posterior models and observed data were considerably reduced when assimilating seismic and production data simultaneously, presenting even smaller errors than production data only cases. This happened for both grids. By adding further 4D information at intermediate layers with the use of two maps, we observed (in both grids) that posterior models could predict important reservoir behaviors, such as the gas trapping in the deeper interval. The coarser grid presented lower well production data misfits compared to the refined grid, but showed to be insensitive to the use of different seismic data in data assimilation, resulting in alike models. Furthermore, the posterior models for the coarse grid presented similar behaviors when performing production forecast, which indicates that the uncertainties may be underestimated in these cases. The refined grid presented slightly greater production misfits but was more sensitive to the different 4D seismic inputs. In this grid, an increased ensemble variance was observed between the posterior models, which is also observed in the long-term forecasts. Also, the most refined grid yielded estimates of acoustic impedance changes visually closer to the observed data than those obtained from the coarser grid. As a real case application, the definition of the best procedure is not straightforward. Results suggest that both grids can be used depending on the project's objective. The coarser grid is a good option for short-term studies, since it is able to properly represent the near future with much cheaper models. The refined grid may be suitable for long-term decisions, because it better represents models' uncertainties and provides safer risk analyses.

Phase Decomposition and Its Applications

We discuss the recently introduced phase decomposition analysis, which entails amplitude variation with time for a specific seismic phase. Assuming a zero-phase wavelet embedded in the seismic data, while flat spots or unresolved water contacts may be seen on the zero-phase component, thin-bed and impedance changes will show up on phase components that are 90° out of phase with the wavelet. Similar bright spots caused by thin hydrocarbon reservoirs are associated with low impedance and show up on the phase component that is −90° out of phase with the embedded wavelet. In all cases the interpretation of bright spots is found to be convenient, and easier with the use of −90° seismic phase component. In this paper, application of phase decomposition to a few instances are first demonstrated through synthetic data examples, followed by a couple of real seismic data case studies. In particular, the case study from a gas storage reservoir in Denmark exhibits how phase decomposition can aid interpretation efforts. Some of the typical issues that seismic interpreters might come across, including the one where the input seismic data might have a phase different from zero phase are elaborated in the ‘Discussion’ section.

Enhanced Discrimination of Seismic Geological Channels Based on Multi-Trace Variational Mode Decomposition

The spectral decomposition is a valuable tool for improving the resolution of seismic interpretation, and thus can improve the accuracy of the subtle geo-features (thin and narrow channels, thin reservoirs, etc.). Variational mode decomposition (VMD) is an adaptive signal decomposition algorithm that non-recursively decomposes multicomponent signals into several band-limited intrinsic mode functions, which is competitive in enhancing time-frequency resolution. However, discontinuity is normally caused by the trace-by-trace process, making the 3D seismic interpretation difficult. To address this issue, we present a novel seismic geological channel detection method for 3D seismic dataset based on multi-trace variational mode decomposition (MTVMD). The proposed method decomposes the broadband seismic data into several intrinsic mode functions and then computes seismic attributes from each component for geological feature analysis. Further tested by field seismic case, the proposed method demonstrates strength in depicting the detailed edges and sedimentary signatures of paleochannels. Overall, the proposed method provides an alternative approach to identifying seismic channels, especially for the detailed portrayals of subtle geo-features in low-quality seismic data.

Investigation of interference from multiple oriented hydraulic fractures while considering near-radial wellbore stress distribution

Stratigraphic sequences are sometimes thin, rarely ideally horizontal and juxtaposed due to faulting. Wellbore trajectories targeting such strata may not be necessarily horizontal aligning with principal stress direction. Perspective from perforation orientations typically embeds understanding of fundamental fracturing issues such as high treating pressure, premature screen-outs, and tortuous and short-circuited fracture paths among others. One or more of these issues may influence other drawbacks making the overall problem more complicated. The objective of this study is to investigate the influence of stress shadow effect of multiple fracture propagation on treating pressure and fracture geometries (apertures, lengths, heights, and tortuosity) then later introduce a new concept of controlling fluid entry into multiple oriented perforations through modification of entry elements combined with radial wellbore technology. The study demonstrates that both simple bi-wing and complex multiple bi-wing fractures are associated with low treating pressure when combination of high phase/high or low orientation angles, illustrated with 1800/900 and 1800/00, is used. It has further shown that oriented perforation reduces the extent of fracture closure zone around the crack mouth. Sequential and simultaneous techniques are implemented with their comparison demonstrating that sequential fracturing is associated with elevated fluid pressure after first injection. A maximum error as low as 0.52 MPa is recorded during the bottom hole pressure analysis. Optimized results from restricted fluid entry elements, simulated within XFEM computational domain capable of accommodating fracture-turning effect, minimized fracture choke-like effect producing relatively uniform fracture development. The new elements are validated against KGD model. The model is further validated against published experiments and Daqing Oilfield data with good match of results in both cases. The study is important for field implementation of hydraulic fracturing in stratigraphically thin reservoirs with well trajectories disoriented from principal stress direction.

Geoelectrical Models of the Achimov Formation Reservoirs at the Tevlinsko-Russkinskoye Field

The article discusses the results of applying the methodology for assessing the oil saturation of the Achimov formation reservoirs based on the quantitative interpretation of electric logging data in vertical wells of the Tevlinsko-Russkinskoye field. Interpretation of electric logging data using traditional methods leads to errors in oil saturation estimation due to complex diagram shapes, which make it difficult to take readings in thin layers under the influence of resistivity-contrasting zones of penetration and enclosing layers. To calculate reservoir properties, approved petrophysical dependencies were applied, and the resistivity value of thin reservoirs was determined as a result of numerical joint inversion of data from a complex of galvanic and induction probes in the class of 2D geoelectric models, taking into account the design features of probes, well structure, radial and vertical distribution of electrophysical properties of rocks in the section. In 24 wells, geoelectric models were built and the oil content of the BS reservoirs was estimated.

Different types of void space and quality of unconventional reservoirs in the Upper Devonian domanic high-carbon deposits of Mukhanovo-Erokhovsky trough (Volga-Ural basin)

Domanic deposits have already been studied in sufficient details. Various aspects of their study were described previosly in many works, but so far, these deposits have been considered mainly as source rocks. Domanic deposits are distributed in a wide stratigraphic range from the Middle Frasnian of the Late Devonian to the Tournaisian of the Early Carboniferous. In this paper, domanic formation is considered as an unconventional reservoir. Due to the complex and heterogeneous structure of rocks, their uneven saturation with organic matter and low porosity values, the methodology for assessing reservoir properties is at a low stage of production. An integrated study of the void space in such deposits, including macro- and microdescription of the core, analytical studies, makes it possible to predict zones with best quality of reservoirs and helped successfullу produce such deposits. In the section of domanic formation were identified the main lithotypes and characterized of each of them. Comparison of the types of void space identified in thin sections and reservoir properties made it possible to classify the main types of reservoirs and assess their quality.

Feasibility Study and Technical Optimization by Implementing Steam Flooding for the Field Development Plan of A Heavy-Oil Field in Yemen

Enhanced Oil Recovery (EOR) applications are highly recommended and required in Yemen to maintain stable levels of oil production. The field selected for this research is located in Yemen, where relatively- thin sandstone reservoirs are dominant at moderate depths. The reservoir is highly undersaturated with an API gravity of 14.2 and a very low solution gas-oil ratio (GOR), initial oil viscosity (uo) of 420 cP. The reservoir is naturally producing with the support of a strong water drive at the bottom, however, the increase in water cut poses a disadvantage for this reservoir. Over time, the oil production will decline and development plans will be required to improve the oil recovery. This research aims to optimize oil recovery factor and the interest in the overall project economy by evaluating the optimization of the steam flood process based on the Stochastic analysis with the highest recovery factor (RF) and the highest net present value (NPV) objective functions. Two optimization techniques have been used to perform the data analysis, deterministic and stochastic approaches. The deterministic approach is carried out by direct analysis on the results of the technical optimization method using the CMG reservoir simulator, while the stochastic approach uses the simulation results from the deterministic approach to determine the most influencing parameter in the steam flood process as well as to optimize the infill and injection wells location, number of steam injection wells and the steam injection rate with the highest oil RF and highest NPV. In this field development using deterministic approach, two producer wells are converted into injector wells. The RF for this initial scenario is 52,34%, and the NPV is 33.10 MM$/STB. For the second scenario using Stochastic approach, CMOST optimization using the maximum RF objective function resulted in RF of 61.33%, and NPV of 43.00 MMS/STB. Finally for the third scenario using CMOST optimization with the maximum NPV objective function resulted in RF of 57.29%, and an NPV of 53.86 MMS/STB. The Stochastic approach with maximum NPV objective function provides the most favorable scenario to be used in the development of Field "AR". And the optimization using the stochastic approach also produces faster, optimum, and more accurate results than the deterministic approach since it forecast a variety of probable results by running thousands of reservoir simulations using many various estimations of economic conditions.

Enhancing vertical resolution with 4D seismic inversion

In this work, we applied a Bayesian time-lapse (4D) seismic inversion to a deep-water heavy oil field located in the Campos Basin (Brazil). In this procedure, the differences of seismic amplitudes of baseline and repeated surveys are the input to calculate the changes in acoustic impedances. To ensure the quality of the results, the parametrization of the inversion was performed by analyzing the anomalies resolution and signal-to-noise ratio with different values of input parameters, and the estimates are crosschecked with the results of a petroelastic modeling applied to the dynamic model. Results show a relevant improvement in the vertical resolution of estimated acoustic impedances in comparison to the amplitude data in a thin reservoir (with thickness ranging from 15 to 45 m). This improvement was possible because of the high-quality of acquired seismic amplitudes (permanent reservoir monitoring) and because of the data variability that is controlled in the Bayesian 4D inversion algorithm. The high resolution of Bayesian inverted results enabled a more detailed vertical zoning of the reservoir, revealing important geological features, such as channels in the main interval and below the reservoir's base, and improved the understanding of the fluid movement over time, enabling the analysis of the injection efficiency and by-passed oil zones as well as the aquifer movement. This information is important to update the static model, by improving the definition of geological features, and to calibrate dynamic models, in the future, by adding the inverted acoustic impedance maps into the data assimilation procedure.

Low-background neutron reflectometry from solid/liquid interfaces

Liquid cells are an increasingly common sample environment for neutron reflectometry experiments and are critical for measuring the properties of materials at solid/liquid interfaces. Background scattering determines the maximum useful scattering vector, and hence the spatial resolution, of the neutron reflectometry measurement. The primary sources of background are the liquid in the cell reservoir and the materials forming the liquid cell itself. Thus, characterization and mitigation of these background sources are necessary for improvements in the signal-to-background ratio and resolution of neutron reflectometry measurements employing liquid cells. Single-crystal silicon is a common material used for liquid cells due to its low incoherent scattering cross section for neutrons, and the path lengths of the neutron beam through silicon can be several centimetres in modern cell designs. Here, a liquid cell is constructed with a sub-50 µm thick liquid reservoir encased in single-crystal silicon. It is shown that, at high scattering vectors, inelastic scattering from silicon represents a significant portion of the scattering background and is, moreover, structured, confounding efforts to correct for it by established background subtraction techniques. A significant improvement in the measurement quality is achieved using energy-analyzed detection. Energy-analyzed detection reduces the scattering background from silicon by nearly an order of magnitude, and from fluids such as air and liquids by smaller but significant factors. Combining thin liquid reservoirs with energy-analyzed detection and the high flux of the CANDOR polychromatic reflectometer at the NIST Center for Neutron Research, a background-subtracted neutron reflectivity smaller than 10−8 from a liquid cell sample is reported.

Monitoring CO2 storage using well-casing source electromagnetics

Successful geologic storage of CO2, whether in a carbon capture, utilization, and storage process or as part of enhanced oil recovery (EOR) operations, requires careful monitoring of the concentration of CO2 within the reservoir. Because injected CO2 is more electrically resistive than the in-situ brines and pore fluids in most storage sites, electromagnetic (EM) methods are well suited to map the distribution of injected CO2 over time. In particular, utilizing existing metallic well casings as electrodes to channel current to formation depth and measuring the resulting electrical and magnetic fields at the surface is an effective technique to image the deep and thin reservoirs of interest. This paper describes the theory behind the well-casing source EM method and discusses a series of field surveys carried out over a three-year period using the method to measure CO2 concentration at an EOR site in West Hastings, Texas. The surveys identify resistive zones that agree with the injection locations and geologic structure of the reservoir and show an increase in reservoir resistivity related to CO2 concentration between the initial field status and the middle survey. However, they also show an unexpected decrease in the resistivity within the reservoir between the last two surveys, which may be due to changes in survey parameters or CO2 injection patterns during that interval.

Experiments and simulations on factors affecting the stereoscopic fire flooding in heavy oil reservoirs

In-situ combustion (ISC) or fire flooding (FF) technology had been widely applicated in developing heavy oil reservoirs. Due to the complex physical and chemical processes, it is not easy to guarantee the high oil recovery. For thin layer reservoirs, vertical well mode of FF can achieve good results, but for thick layer reservoirs, the vertical producing degree of FF under vertical well pattern is low. Therefore, it is necessary to deepen the basic understanding of fire flooding under different well patterns and study the influencing factors for thick heavy oil reservoir. Stereoscopic fire flooding (SFF) mode is proposed in this paper, and the one-dimensional combustion tube and differential scanning calorimetry (DSC) experiments were introduced and designed. The heavy oil samples of G block in Liaohe oilfield in China were studied and the oxidation kinetic parameters were obtained by experiments. The applicability of oil samples for fire flooding was tested. The different fire flooding modes was compared and the influencing factors of SFF were analyzed through simulations. The results indicated that the temperature of high temperature oxidation (HTO) was above 450 °C. The CO2 content of the produced gas was more than 13% and the apparent HC atomic ratio was 1.28. DSC experiments showed the activation energy of HTO stage was 1.40 × 105 J/mol. The results indicated that the heavy oil samples can reach a high temperature combustion state. The SFF mode was simulated by CMG-STARS module based on the experimental results. The simulation results showed that SFF had better performance than FF of only vertical wells in oil recovery. The important factors of SFF, such as gas-injection rate, reservoir thickness, transverse permeability, vertical permeability, crude oil viscosity, formation dip angle and relative position of horizontal wells and the applicable conditions of SFF mode were analyzed and the optimum condition for SFF mode for each influencing factor was analyzed, and the conclusions were obtained.

A target-oriented integrated workflow for seismic delineation of thin tight reservoirs in the eastern Sichuan Basin, China

Complex lithology association along vertical direction results in thin layers with different interbed patterns of the Lower Triassic Jialingjiang Formation (T 1 j), Sichuan Basin. The prediction of thin tight reservoirs in the Jialingjiang Formation is important for further oil and gas exploration. However, seismic data in the eastern Sichuan Basin has poor lateral continuity of seismic events because of strong interference noises, which makes it difficult to pick horizons. Moreover, low dominant frequency (<25 Hz), low seismic resolution, and weak response characteristics of strong transverse heterogeneity on logging parameters make it challenging for the thin reservoirs prediction. To tackle these issues, in this study, we propose a target-oriented workflow by integrating seismic data processing with interpretation to delineate the thin reservoirs and corresponding hydrocarbon production capacity. In the processing workflow, we first remove the noise interferences using the structure-oriented filtering (SOF), which can improve the effective information of seismic events and also preserve the features of fault structures. Second, we propose a novel method based on spectral shaping and sparse inversion to enhance the seismic resolution. Tests on filed data demonstrate that the effective information and resolution of processed seismic data are significantly enhanced. Then, in the seismic interpretation, fluid mobility and spectral decomposition are first used to delineate the spatial distribution of favorable reservoirs. Furthermore, multi-attribute integrated interpretation involving impedance analysis, reservoir thickness estimation and porosity inversion is used to evaluate the storage capacity and productivity of the thin reservoirs. The estimated impedance, reservoir thickness and porosity show good agreement with well information, demonstrating the feasibility of the proposed method for accurately predicting thin reservoirs in this area. Multi-attribute integrated interpretation revealed that the favorable thin reservoirs are mainly developed from the northeast to the southwest in the study area, which can provide effective guidelines for future production well drilling and distribution delineations of a favorable reservoir in the Eastern Sichuan Basin. • Structure-oriented filtering (SOF) can remove noises and enhance the effective continuities and structural features. • A new resolution enhancement (RE) method improves the seismic resolution significantly and reduces the artifacts. • The target-oriented processing workflow can markedly improve the quality of the seismic data. • Multi-attribute analyses indicating the favorable thin reservoirs is developed for the target zone.

Application of new geosteering technology in thin reservoir

Because some oilfields in China belong to the thin bottom water reservoir model, the actual drilling process is technically difficult. In order to ensure the maximum drilling operation of the target layer and the basic development effect of the oilfield, technicians should introduce advanced steering tools and study new geosteering technology to fundamentally ensure the exploitation quality of thin oil reservoirs.After exploring the introduction of new geological guidance technology in detail, this paper further explores the principle of new geological guidance technology, and summarizes the application strategy of new geological guidance technology combined with the development of thin-layer reservoir.

Study on Class 3 reservoirs infill adjustment methods

The exploitation object of the Class 3 reservoirs of infill adjustment well pattern is SaPu thin and poor oil reservoir and Gaotaizi oil reservoir. The remaining oil potential of thin and poor oil reservoir and untabulated reservoir is brought into full play to the maximum extent, which is the focus of this infill adjustment. Therefore, it is necessary to carry out effective research on the formulation of mining plan, the dynamic change law of new and old wells from plane connection to vertical sedimentary units, and the tracking and adjustment of surrounding wells. First, according to the change law of sand body control degree in different oil layers and different well spacing, combined with the remaining oil distribution characteristics of Class 3 reservoirs of Sapugao oil layers, the well pattern and well spacing are optimized. The second is to study the complex well pattern, well location relationship and its matching adjustment timing. Through the structural adjustment of the infill well pattern of the Class 3 reservoirs in plane and vertical combination, A set of adjustment and tapping technology of the infill well area of the Class 3 reservoirs is formed, which gives full play to the remaining oil potential. Compared with the expected single well daily oil production of the typical region increases by 1.2t, water cut decreases by 2.8 percentage points, and the natural decline is - 10.22%. The research results of this innovative well pattern infill combination method and potential tapping method of matching adjustment have certain reference significance for guiding the adjustment and potential tapping of infill well area of Class 3 reservoirs in water drive.