Abstract

For production in unconventional plays, it is a common practice to stimulate a well with equally spaced multi-stage hydraulic fracking as long as the bore hole is positioned within the target. However, it is not uncommon to observe significant production variations in the horizontal wells in the same fields with similar length and stimulation design, let alone wells drilled in different formations.

Integration of mineralogical and elemental composition data from drilled cuttings and real-time mud gas measurements serves as a key component to identifying sweet spots and to optimize stimulation in unconventional reservoirs. In the following case study of the Devonian play in Oklahoma, two wells drilled in two different formations were logged acquiring rock composition from drilled cuttings and mud gas data. Drilled cuttings were collected in the horizontal section utilizing optimized sample collection protocol. Mud gas data was acquired utilizing an extractor at the shale shaker coupled with a chromatograph.

The two different formations exhibited different rock compositions. This was determined by their respective mineralogical and elemental fingerprints. Minerals linked with higher frackability were found in different proportion in the two formations. Moreover, distribution of minerals in the lateral section drilled in each formation showed variations that helped delineating the intervals of higher frackability.

In addition, rock compositional data helped confirm any deviation away from targeted zone. This observation was further supported by variations in mud gas trends.

Association of frackability with elements linked to organic matter rich intervals and mud gas data acquired in the two formations indicated that while one formation required equally spaced multi-stage fracking, the other formation required optimized fracking design for completion and production.