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The analysis and prediction of pressure conditions in the subsurface ahead of the drill bit and while drilling is a critical aspect of the exploration process. Geopressure analysis uses geophysical data from seismic or logging sources to estimate the confining stress, pore pressure and other parameters that are critical to proper basin modeling, prospect analysis and well completion. The workflow for accurate and robust geopressure analysis must include a high level of integration and expertise in seismic analysis, log analysis and well performance analysis. Our leading-edge geopressure experts provide robust solutions that can be easily integrated back into the interpreter workstation for use by the exploration team. Fusion offers superior solutions in geopressure that will enhance your exploration efforts and dramatically reduce your drilling and completion costs.
Fusion offers an integrated suite of geopressure services in the following areas:
Geopressure is a critical property that must be understood to achieve success in your exploration and production efforts. Fusion has assembled the finest team of pressure experts in the industry. We believe that Fusion can offer superior solutions in geopressure that will enhance your exploration efforts and dramatically reduce your drilling and completion costs. Geopressure analysis is directly applicable to the following problems:
Basin Scale Modeling & Prediction
Understanding the pressure regimes in sedimentary basins is a fundamental part of the exploration process. The pressure regime is a primary forcing agent in the maturation and migration of hydrocarbons, and their ultimate trapping in reservoirs that are reachable with the drill bit. Fusion provides integrated geopressure analysis at the basin scale as part of our integrated interpretation services. Geopressure analysis at this scale usually uses 2D seismic data or 3D if available and any well information that is available for the basin. In cases where no well control is available, a qualitative assessment of the pressure regime using seismic velocities can still yield valuable insights into the hydraulic system of the basin, and can guide the explorationist to better judgment about the robustness of the petroleum system so that better economic assessments can be made for licensing rounds and regional exploration.
Understanding the hydrogeology and pressure regime of a prospect is critical to developing a clear picture of how fluids are migrating and being trapped in the prospect. Unfortunately, most prospects are developed without this critical information, which leads to a significantly larger number of dry holes in wildcat drilling. Fusion offers prospect-scale pressure analysis as the next step in understanding the pressure regime of the basin as the exploration team refines its targets in preparation for drilling. Prospect scale pressure analysis is typically done on 3D data and uses dense velocity analysis and the REVEL™ process to obtain a detailed velocity structure that can be mapped into pressure using Fusion´s proprietary tools and expert knowledge. The result of such a pressure analysis is a detailed 3D pressure map of the subsurface that can be integrated with hydrogeologic flow modeling to determine the hydraulic behavior of the geological system, and better predict where hydrocarbons will migrate and be trapped, and whether regional and local seals will hold the hydrocarbon accumulations.
Final REVEL™ velocity field generated from pre-stack seismic data for the prediction of geopressure (after Huffman et al, 2003)
Final pore pressure gradient field generated from the REVEL™ velocity field (after Huffman et al, 2003). Pressure gradient values are in equivalent density units.
Final fracture pressure gradient field generated from the REVEL™ velocity field (after Huffman et al, 2003). Pressure gradient values are in equivalent density Geopressure Prediction in Unloading Environments
Pressure prediction is often performed in environments where multiple pressure mechanisms are active including unloading and secondary chemical compaction. In such environments, a more sophisticated methodology is required. Fusion offers this methodology with our proprietary GEOPRESS™ 3D prediction tool. GEOPRESS™ has the capability to handle multi-mechanism calibration and apply these multiple calibrations using seismically mapped horizons to bound the top and base of each calibrated regime. The following examples show applications of this advanced method that allows the prediction process to honor robustly the correct physics for each pressure mechanism, which yields superior results compared to other approaches.
Final REVEL™ velocity field for a survey in the Woodbine play in central Texas. Note the significant velocity reversal as the Woodbine section is buried more deeply to the left side of the section.
Final pore pressure gradient generated from the REVEL™ velocity field using a multi-zone calibration for undercompaction in the shallow section and unloading caused by hydrocarbon maturation in the Woodbine section.
Final fracture pressure gradient generated from the REVEL™ velocity field using a multi-zone calibration for undercompaction in the shallow section and unloading caused by hydrocarbon maturation in the Woodbine section.
Final REVEL™ velocity field for a survey in Matagorda County, South Texas. Note the behavior of the velocities as they follow the fault blocks.
Final pore pressure gradient generated from the REVEL™ velocity field using a multi-zone calibration for undercompaction in the shallow section and unloading and secondary compaction in the deep section from Matagorda County, Texas
Final fracture pressure gradient generated from the REVEL™ velocity field using a multi-zone calibration for undercompaction in the shallow section and unloading and secondary compaction in the deep section from Matagorda County, Texas
Velocity and pore pressure prediction panels for well ``A´´ in the previous figures. The blue stars are the mud weights used to the drill the well. Note the overbalanced condition in the mud weights at 9,000 and 11,000 ft, which were confirmed by a dramatic decrease in liberated gas on the mud log through this interval.
Velocity and pore pressure prediction panels for well ``B´´ in the previous figures. The blue stars are the mud weights used to the drill the well. The orange stars are influx pressures. Pre-Drill Prediction of Reservoir Pressures
The prediction of pore pressure and fracture gradient ahead of the drill bit is one of the most critical tasks in planning a well. With deepwater well costs running upwards of $50 MM per well, this process should never be taken lightly as it can save the operator millions of dollars in avoiding a single well intervention or pressure event. Fusion offers its pressure prediction services as part of the planning process, and Fusion´s world-class experts work with the client´s drilling engineers to help them understand the results of this process. Fusion´s experts have over 100 years of experience in predicting pressures for well planning in a wide range of petroleum basins from around the world. We use our depth of expertise and global experience to provide our clients with robust pressure solutions that save them significant amounts of money and pressure-related downtime on their wells.
Of particular concern in pre-drill planning is the role of reservoir pressures in well performance. The advent of the structural hyper-pressuring concept (also known as centroid theory) led Fusion to develop an innovative and unique approach to the modeling of reservoirs during pressure prediction that allows for the prediction of reservoir pressures at the specific penetration point for a given well. The theory also allows for more accurate prediction of column heights pre-drill and assessment of seal failure risk.
Determination of mud program and casing program for a case where only shale pressures are considered (left panel), and the same model with three reservoirs included in the plan (right panel). Note that the penetration points on each reservoir are significantly higher than the centroid, which results in significantly higher reservoir pressures relative to the background shale pressure at the depth that the reservoir is penetrated. In this case, the mud program must be designed to handle the highest pressures expected for the potential saturating fluids. The lowest pressures will be for brine saturation, with progressively higher pressures for oil and gas respectively. Note also that the increase in mud weight required to manage the reservoir pressures causes a significant overbalance condition in the shales above and below the reservoir interval. This overbalance condition can cause stuck pipe, and also decreases the ROP in the shales, thus raising the cost of the drilling operation. The changes in the mud program also cause changes in the casing program with two additional casing strings required to drill the same well.
An important part of the pressure prediction process is to analyze the results of each well as they are drilled. This analysis helps to improve the understanding of pressure regimes in and around petroleum prospects, and also improves the calibration process for pressure prediction related to future wells. Fusion offers post-drill analysis to our clients as an extension of our pre-drill pressure prediction process. The post-drill analysis allows the client to learn more about the pressure regime of their prospects, and can also help the geoscience team better assess the economic viability of prospects that may be marginal in size after the first exploration wells are drilled. The post-drill analysis also closes the loop on the pre-drill process and allows an assessment of the true error bars on the pressure prediction in areas where little to no calibration information existed before the well was drilled. The post-drill analysis can also integrate the learnings from previous wells with the planning for future wells so that difficult drilling zones, unusual formation properties and other adverse drilling conditions can be properly evaluated and understood in future wells to mitigate the risk of problems related to those conditions. |
