The purpose of this work was to determine the effects of induced fractures on overall reservoir performance during primary as well as secondary performance. The ultimate objective of this continuing study is to optimize ultimate recovery from tight carbonate reservoirs in which high pressure water injection is the only economically feasible secondary recovery technique.
The influence of fractures on secondary performance has been emphasized in much of performance has been emphasized in much of the industry literature. This report emphasizes that inflow performance data on individual wells can be used to determine the presence of waterflood-induced fractures. presence of waterflood-induced fractures. This documentation is limited to qualitative case studies of two Clearfork reservoirs situated on the Central Basin Platform in West Texas (see Exhibit I). The Platform in West Texas (see Exhibit I). The Monohans Clearfork Waterflood is a one hundred percent Shell-operated project located in Ward percent Shell-operated project located in Ward and Winkler Counties, Texas. The TXL North 5600'/Tubb Unit is a Shell-operated waterflood project located in Ector County, Texas. Both project located in Ector County, Texas. Both projects are in tight, poorly-developed, projects are in tight, poorly-developed, heterogeneous dolomite reservoirs which fracture vertically.
The most significant conclusion reached from this study is that the azimuthal orientation of induced vertical fractures greatly influences the primary as well as secondary performance of tight, discontinuous carbonate performance of tight, discontinuous carbonate reservoirs. A secondary inference is that induced fractures in the Clearfork reservoirs on the Central Basin Platform are oriented normal to structural trend.
This report consists of retrospective analyses of the aforementioned carbonate reservoirs where waterflooding is currently being used to enhance ultimate recovery. Azimuthal orientation of induced fractures in the Monohans Clearfork and TXL North 5600'/Tubb reservoirs were determined empirically.