The Eagle Ford at Chittim Ranch in the Maverick Basin has long been recognized for its tremendous amount of original oil in place (OOIP). To unlock the true potential of this reservoir, an exploration and development company began a 3-year study to design and implement an enhanced-oil-recovery (EOR) project using huff ’n’ puff (HnP). However, unlike many EOR/HnP projects that use field gas, the company targeted another source of injectant: Y-grade. This is the largest undertaking of a Y-grade injection project known to the authors.
Introduction
The geologic setting within Chittim is best summarized as a Cretaceous thrust structure (Chittim Anticline) that overlies a narrow Jurassic rift basin (Fig. 1 above). However, it is within a complex depositional and tectonic history that the lower Eagle Ford interval experiences expansion, thermal maturation, and uplift to an accessible present-day depth of approximately 2,500–6,000 ft below the surface. Oil gravity ranges from 28 to 40 °API. The quality of the Eagle Ford on the Chittim can be characterized by the amount of OOIP, which is approximately 68 million bbl per section.
