Attic Thin Oil Columns Horizontal Wells Optimization Through Advance Application of ICD's and Well Placement Technologies in South China

摘要

The horizontal wells side-track campaign at CACT's H fields in South China Sea has been very successful and challenging over the last, two years. Horizontal wells are well-recognized in developing thin-oil column within multi-stacked reservoir by exposing wellbore to maximum reservoir contact and drainage area. The lateral targets and remaining oil reserves are in attic thin oil columns in clean sands and shaly sands. Since the oil column is thin at the top of a clean sandstone reservoir with strong bottom water drive, early water break through can occur even when the lateral is well placed on the top of the reservoir. To further optimize the reserves recovery, horizontal trajectories are placed near the top of the reservoir, and the well is completed with stand-alone screen combines with downhole inflow control devices (ICD's). This combination provides the horizontal well optimum completion for draining and further prolongs the life of the well. The application of the field-adjustable nozzles based on real-time Logging-while-Drilling (LWD) data updates into ICD's predrilled model, together with the precise well placement have enabled horizontal wells to be economically developed in a thin oil-bearing layer. In this paper, some of the technical assessment and collaboration workflow between the multi disciplinary team of technology users and service providers, enrooting to the successful implementation of the first nozzle-type ICD's installation and Distance-to-Boundary Well Placement technology in China will be highlighted. The success of the first ICD's well completions installation was proven with better Productivity Index (PI) based on initial well performance. The first ICD's well produced —100% oil for almost two months since early Mar 2009. Meanwhile, a second ICD's well with thinner net oil pay produced 100% oil for 20 days clearly showed the benefit of ICD later when water break through and increased to 85%. The mentioned integrated Nozzle-ICD's design with precise Distance-To-Boundary Well Placement solution have shifted the conventional application of !CD's, which is hardware-orientated, from being dictated one-way by hardware supplier, towards a holistic reservoir-centric design. It has become an operation that keeps all-party informed and always in communication. The "real-time" add-value of LWD and well placement data in updating the predrilled ICD's well model has benefitted horizontal wells inflow control design. This integrated and reservoir-centric solution has optimized horizontal well application successfully in one well, but facing some reservoir and structural challenges in another well; which has provided valuable lesson-learned for future drilling.