Efficient Approach for Optimal Well Placement to Optimize the Underwater Distributary-Channel Laminated Reservoir Development in Offshore South China
Abstract: Development of a green oil field was started in 2014 with a horizontal well pattern targeting the underwater distributary-channel sand reservoir of the braided-channel deltaic sediment. In this geological environment, the complex uncertainties appear as the irregular superposition of sand bodies and interbeds, lateral changes in sand reservoir property and thickness, and the high structural dip uncertainty. In appraisal wells, the laminated edge water sand reservoir consists of multiple irregular and thin (0.5… Show more
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High-Definition Deep-Looking Inversion Integrated Service Set Golden Spikes to Push Lithological Reservoir Development Limit
Development of lithological reservoirs is becoming vital in the Pearl River Mouth basin of the South China Sea. One of these is the Neogene M lithological reservoir in which the deposition of a paleodelta over multiple periods caused a complex profile including severe heterogeneity, rapid lateral property change, poor sand connectivity, and irregular thickness variation (0.5 to 12 m) with interbeds. The current development scope is approaching the predicted eastern sand-pinchout line, making it necessary to identify key points as "golden spikes" to shape the sand bodies’ spatial distribution profile, internal characterization, and pinchout points. based on the sand bodies’ distribution network, drilling and production techniques can be specifically configured to push the development limit as much as possible by efficiently squeezing remaining oil. In the horizontal well campaign, five appraisal wells are important golden spikes where interwell structural and stratigraphic uncertainties are high due to limited resolution of 3D seismic and sequence stratigraphic data and limited depth-of-investigation (DOI) of conventional logging data. A high-definition deep-looking inversion service was identified to balance resolution and DOI. This novel inversion stochastically analyzes hundreds of formation models using the Metropolis-coupled Markov-chain Monte-Carlo method and then identifies multiple layers (more than three) with 6 m DOI, formation resistivity, anisotropy and dip. With the key resolution-DOI balance, this deep-looking inversion can reveal high-definition interwell details and set a series of golden spikes to identify sand superposition configuration and pinchout points. Within the refined 3D reservoir model, the geo-steering efficiency, completion configuration, and waterflooding stimulation efficiency could be optimized for maximum recovery. Furthermore, a reasonable well pattern arrangement could be developed to sweep the predicted remaining oil and progressively push the development limit. As evident from ten horizontal wells, high-definition interwell reservoir details were revealed by describing up to four boundaries and five layers simultaneously within maximum 5-m distance from borehole. The golden spikes characterized sand bodies’ profile and their pinchout points. Compared to the prognosis, the southeast margin has been moved to the west. Smooth trajectories were proactively steered to chase irregular sand bodies with minimal loss. Based on the refined 3D reservoir model, proper completion configurations were designed to accommodate the variable properties in this reservoir. One horizontal water-injection well focused on specific discontinuous sand bodies for an average 1.6MPa (megapascal) /well pressure recovery and total 126,000 barrels/year incremental oil. Oil recovery reached 13% within 3.5 years of production, faster than the prognosis. Under current development led by this integrated service, four wells were planned towards updated eastern pinchout line to exploit the remaining oil as much as possible. With increasing distance from the platform, laterals can be placed accurately to achieve objectives with high drilling efficiency and less drilling risk by minimizing unnecessary trajectory adjustments. From resolution-DOI balance to the identification of golden spikes, this deep-looking inversion could constrain 3D seismic and sequence stratigraphic interpretation to refine the large-scale reservoir model. Considering drilling and production methods, this integrated service could effectively push the development to the potential limit.
High-Definition Deep-Looking Inversion Integrated Service Set Golden Spikes to Push Lithological Reservoir Development Limit
Development of lithological reservoirs is becoming vital in the Pearl River Mouth basin of the South China Sea. One of these is the Neogene M lithological reservoir in which the deposition of a paleodelta over multiple periods caused a complex profile including severe heterogeneity, rapid lateral property change, poor sand connectivity, and irregular thickness variation (0.5 to 12 m) with interbeds. The current development scope is approaching the predicted eastern sand-pinchout line, making it necessary to identify key points as "golden spikes" to shape the sand bodies’ spatial distribution profile, internal characterization, and pinchout points. based on the sand bodies’ distribution network, drilling and production techniques can be specifically configured to push the development limit as much as possible by efficiently squeezing remaining oil. In the horizontal well campaign, five appraisal wells are important golden spikes where interwell structural and stratigraphic uncertainties are high due to limited resolution of 3D seismic and sequence stratigraphic data and limited depth-of-investigation (DOI) of conventional logging data. A high-definition deep-looking inversion service was identified to balance resolution and DOI. This novel inversion stochastically analyzes hundreds of formation models using the Metropolis-coupled Markov-chain Monte-Carlo method and then identifies multiple layers (more than three) with 6 m DOI, formation resistivity, anisotropy and dip. With the key resolution-DOI balance, this deep-looking inversion can reveal high-definition interwell details and set a series of golden spikes to identify sand superposition configuration and pinchout points. Within the refined 3D reservoir model, the geo-steering efficiency, completion configuration, and waterflooding stimulation efficiency could be optimized for maximum recovery. Furthermore, a reasonable well pattern arrangement could be developed to sweep the predicted remaining oil and progressively push the development limit. As evident from ten horizontal wells, high-definition interwell reservoir details were revealed by describing up to four boundaries and five layers simultaneously within maximum 5-m distance from borehole. The golden spikes characterized sand bodies’ profile and their pinchout points. Compared to the prognosis, the southeast margin has been moved to the west. Smooth trajectories were proactively steered to chase irregular sand bodies with minimal loss. Based on the refined 3D reservoir model, proper completion configurations were designed to accommodate the variable properties in this reservoir. One horizontal water-injection well focused on specific discontinuous sand bodies for an average 1.6MPa (megapascal) /well pressure recovery and total 126,000 barrels/year incremental oil. Oil recovery reached 13% within 3.5 years of production, faster than the prognosis. Under current development led by this integrated service, four wells were planned towards updated eastern pinchout line to exploit the remaining oil as much as possible. With increasing distance from the platform, laterals can be placed accurately to achieve objectives with high drilling efficiency and less drilling risk by minimizing unnecessary trajectory adjustments. From resolution-DOI balance to the identification of golden spikes, this deep-looking inversion could constrain 3D seismic and sequence stratigraphic interpretation to refine the large-scale reservoir model. Considering drilling and production methods, this integrated service could effectively push the development to the potential limit.
Quantitative Production Steering through High-Definition Boundary Detection Service for the Sustainable Development of the Bottomwater Reservoir
In the northern part of the South China Sea, P oilfield entered the mature stage with a high water cut. As an important contribution to the sustainable development of this field, a horizonal infill campaign targeted the unexploited areas for their valuable remaining oil for improving oil recovery. However, the sparse well control and low-resolution seismic data induced high uncertainties regarding the structural profile, reservoir properties, effective oil column, and remaining reserves with the bottomwater drive in the infill well area. These uncertainties greatly affected the production steering efficiency in the complex reservoirs and well performance, which cannot be effectively addressed by the conventional logging and modeling technologies. Predrilling modeling results and global successful cases could increase operators the confidence in using the high-definition boundary detection service (HDBDS) for achieving well objectives. Without any artificial assumptions, HDBDS could provide the stochastic resistivity inversion to remotely identify the quantitative subsurface features, including layer numbers, resistivity and anisotropy distribution, thickness, and dip. In the specific operation area, the inversion can detect the reservoir features up to 3 m from the borehole, which could quantitatively reconstruct the subsurface profile to efficiently guide the horizontal geosteering operation for maximum standoff from the water zone. Furthermore, the production steering can be enhanced through optimizing the corresponding water-controlled completion configurations. During the real-time execution of the horizontal infill wells with an approximate 500- to 600-m section, HDBDS inversion could map the effective boundaries with a distance of up to approximately 3 m, including reservoir top and bottom, water zone top, as well as some interbed boundaries. Combining conventional measurements and HDBDS inversion, the subsurface model was quantitatively reconstructed with the obvious deviations from the original elements. Subsequently, the horizontal wells were precisely controlled for enough oil column, even with a shorter production interval than prognosis in some wells. In the updated reservoir model, the inflow control device (ICD) water-controlled completion configuration was specifically optimized to delay bottomwater breakthrough. As a result, the effective production steering was achieved, with the actual well performance better than expected. Furthermore, the oil trap column and remaining oil reserves could be reassessed to evaluate the production potential and further development direction in this field. Generally, HDBDS inversion could update the quantitative model to induce the production steering, which was valuable to contribute to the sustainability of this bottomwater field in the deep-development stage.
Resistivity-Inversion-Derived Workflow from the Subsurface Uncertainty Management to the Quantitative Reservoir-Scale Profile Update and Well Placement in Reservoirs with Diverse Complexities
At the in-depth development phase, the current horizontal infill campaign in H oil field targets reservoirs with high remaining oil potential and the diverse complexities subject to both structural and lithological controls. These structural and lithological reservoirs are characterized by the uncertainties of formation dip and oil/water contact (OWC), severe stratigraphic heterogeneity, lateral properties change, poor sandstone connectivity, and thickness variation (less than 5 m) of the oil column and interbeds. To effectively squeeze the potential remaining reserves, the scope of the current infill campaign mainly encompasses: (1) the limited crests of the anticlinal traps with uncertain oil column and lateral changed reservoir, and (2) the unexploited marginal areas close to the reservoir pinchout line. Accordingly, it is necessary to quantitatively update the reservoir-scale subsurface profile and execute well placement operations by addressing the above uncertainties with individualized services and workflow. In these diverse reservoirs, interwell structural and stratigraphic uncertainties are high because resolution of large-scale seismic data and depth-of-investigation (DOI) of small-scale conventional logging data are limited. On these grounds, a high-definition boundary detection service (HDBDS) was employed, which can provide a stochastic resistivity inversion to remotely identify quantitative subsurface features with DOI up to 6 m and resolution of approximately 1 m. Its advantage of balancing resolution and DOI can induce the accurate description of high-definition interwell details, including formation superposition configuration, reservoir pinchout points, and dynamic OWC. Furthermore, HDBDS inversion can combine 3D seismic data and conventional logging data to effectively induce the workflow from subsurface uncertainty management to the quantitative reservoir-scale profile update and well placement. HDBDS inversion-derived workflow effectively contributed to us achieving our objectives of this infill campaign by generally revealing the high-definition reservoir profiles along the horizontal sections. Up to four boundaries and five layers were mapped simultaneously with a maximum of 3 m distance from the borehole. High coverage and probability of the updated quantitative features induced the higher reservoir profile update rate in these specific environments than that based on the conventional services. In the complex developed areas mainly subject to both structural and lithological controls, the reservoir top, lateral changed properties, and dynamic tilted OWC were quantitatively inverted to identify the effective 1.5- to 3-m oil column, lower than prognosed 5-m column. In the lithological-control reservoirs at block margins, formation superposition configuration, pinchout points, and lateral properties changing features were clearly delineated. Accordingly, the quantitative well placement operations were efficiently executed to distribute the actual smooth trajectory connecting multiple sandstone bodies with the less risk, as well as with maximum standoff to the tilted OWC. The quantitative results from the inversion-derived workflow could further optimize the completion configuration, waterflooding stimulation efficiency, and well pattern to push development limits as much as possible by efficiently squeezing the remaining oil in these complex structural and lithological reservoirs.
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