This article is based on results of drilling wells in Yuri Korchagin field. Interpretation of the obtained data derived the conclusions that will help to stake future wells in better geological conditions and minimize risks during construction of wells.
This paper demonstrates the approach to field development that involves geomechanical expert analysis at early stages of planning and development. One of the most important problems raised today by geomechanics experts is late involvement of geomechanical analysis and review in the field lifecycle and its usual occurrence only at the development stage. Such approach might lead to a significant reduction in the spectrum of solutions and opportunities to be used in drilling and subsequent production.
The need for geomechanics was identified early at the stage of the field development plan preparation for the V. Filanovsky Field, the largest in the North Caspian Region. Mindful of the complexity of the geological and drilling conditions of the field area, geomechanical modelling was conducted a 3D geomechanical model was built that made it possible to estimate the borehole stability of the designed wells.
The 3D geomechanical model served as a "foundation" for preparation of a field Basis of Design. It helped to identify the key elements: well design, optimized well paths taking into account the geology and unstable intervals, potential risks, multilateral well sidetracking points, drilling mud type and mud weight, etc.
As a result of an extensive multi-year study, the drilling was performed based on pre-selected and pre-computed parameters along the optimized trajectories planned as per the 3D geomechanical model. To additionally reduce potential risks, the drilling process is accompanied by real-time geomechanical calculations, the purpose of which is not limited to update of safe mud weight window model on the basis of real time data but also includes control of borehole stability, hole cleaning, differential sticking risk, cavings morphology, controlling of equivalent circulation and static density within the safe window, well path update for drillability in case of adjustments. Logging while drilling provides of critical information for permanent update of the geomechanical model and improvement of functions, which allows further optimization of well paths and the most accurate parameters of the "safe mud weigh window".
Geomechanics involvement at the Basis of Design project preparation allowed early exclusion of instability risks and identification of well drilling features that would be impossible to implement at the development drilling stage. The result currently achieved by the above effort is the possibility of drilling absolutely all wells, including extended reach (ERD) wells, without any wellbore instability-related problems. Further changes in the modelling approach will be associated to improvement of related functions to ensure still safer and faster drilling.
A reservoir optimization group has currently been formed to support the field development. The next step in the development of the geomechanical model of the V. Filanovsky field will be coupled geomechanical and reservoir modelling to make it possible to assess the impact of production on the strain-stress state of the formation and, therefore, on the reservoir properties. Updated model will also be used for planning multi-stage hydraulic fracturing in relevant wells.
Construction of offshore exploration wells in harsh pressure and temperature environment involves a high risk of geological complications. This is particularly relevant for exploration operations in insufficiently explored areas where the well design is based on seismic data, while the nearest drilled wells are at a considerable distance and do not reflect the specific geological conditions at the point of the new target. This paper presents a comprehensive approach to the detailed study of the geological structure of the Caspian shelf exploration area by processing 3D seismic data for the purpose of forecasting and monitoring hydraulic fracturing pressure and pore pressure prior to construction and during well drilling. Optimized algorithm of data processing in a 7×7 km near-wellbore seismic volume, including detailed tomographic analysis using the Seismic Guided drilling (SGD) method, real-time updating of the geomechanical model, updating of the structural framework and forecasting of properties allows to effectively reduce risks during well construction. Taking into account the experience of geological complications during drilling through Neogene and Quaternary sediments in North Caspian it is also shows the application and integration of geotechnical engineering survey data to refine the upper section model.
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