In the broad M deepwater gas field, a horizontal well project was initiated to develop a virgin gas reservoir H. Several appraisal wells constrained the seismic-derived reservoir model to discover the resistive reservoir overlapped by a very thick shale formation without clear markers inside. Efficient reservoir development comes from a soft landing within the defined target area and productive horizontal drilling close to the reservoir top. However, various uncertainties affected the development efficiency, such as the thickness of the puzzling overlying formation, reservoir top position, lateral reservoir property changes, and structural dip.
Individualized reservoir mapping services with different scales were employed to cost-effectively achieve the specific development objectives by remotely revealing multiscale formation profiles around the borehole, including multiple key boundaries, formation properties, and possible fluid characterization. With high depth-of-investigation (DOI) up to 30 m from the borehole, an ultradeep reservoir mapping service (UDRMS) could remotely detect the resistive gas reservoir from the overlying conductive shale formation in the deviated landing section, as well as delineate an intrinsic layering of contrasting resistivity within the reservoir, which can strategically instruct the productive horizontal drilling. Accordingly, a high-definition boundary detection service (HDBDS) could cost-effectively enhance the production steering efficiency with a DOI of approximately 5 m and a resolution of approximately 1 m.
In deviated landing sections, from puzzling shale zones, with the help of UDRMS answer products, the approaching reservoir tops were remotely detected with 20- to 25-m true vertical depth (TVD) distance, identified from 3- to 13-m deeper than prognosis. Then, the soft landing near the validated reservoir tops was achieved without the horizontal section being wasted. Furthermore, the reservoir profiles were finely revealed, including the gas/water contact and vertical heterogeneity, which greatly instructed the further horizontal production steering by using HDBDS inversion answer products. Moreover, the actual gas production was approximately 20% over prognosis.
The combination of multiscale UDRMS and HDBDS proved to be strategy-changing for cost-efficient deepwater reservoir development by individualized reservoir-scale model refining in time.