Historically, application of open hole gravel packs have mainly been limited to completion of deviated and vertical wells. Other limiting factors affecting selection of this type of completion are reservoir quality and heterogeneity, or the need for selective completion. However, with an increasing number of high angle and horizontal wells being drilled, the industry is focusing more attention on how to use gravel packs to greater effect in long heterogeneous sections. Keys to success are productivity, management of formation damage through optimal filter cake design, and attainment of long term sand control by ensuring complete gravel placement over the entire producing interval.
This case history discusses a high angle open hole gravel pack application for a sand shale sequence. Inhibition of these highly reactive intra reservoir clays was achieved using a low solids formate based mud system. Full gravel placement along the high angle (75°) reservoir section was accomplished using an alternative path gravel pack technique. Filter cake removal, unlike other industry approaches using acids, relied on application of enzymes to enhance the cleanup/back production of filter cake through the oversized gravel and so maximise productivity.
The discussion will focus on the system design approach to drill-in fluid design / clean-up, and the actual gravel pack placement. Finally, the productivity performance, as deduced from pressure transient analysis, will be presented to demonstrate the success of the unique clean-up approach adopted for this operation.