Real-Time Advanced Mud Returns Flow Analysis Combined With Advanced Mud Gas and Elemental Analysis on Drill Cuttings Aids Fracture Detection and Interpretation in Unconventional Reservoirs: A Case Study

Abstract

Identifying and interpreting presence of fractures in the formation while drilling has always been a challenge. In conventional reservoirs, open fractures could infer higher porosity, permeability and accumulation of hydrocarbons which are beneficial to higher production but also point to potential drilling hazards causing loss circulation or potential influx. In unconventional reservoirs, presence of open fractures could enhance the effectiveness of hydraulic stimulation and hydrocarbon production. However, they could also indicate connectivity of fracture networks to potentially water producing layers, alongside oil or gas.

Fracture detection while drilling has been an evolving subject of discussion in recent years. The operators have been relying on conventional methodology of running downhole wireline logging tools to detect and interpret fractures to characterize the reservoir, which could be expensive, intrusive and very challenging in long lateral trajectory wells bores. Fracture detection, while drilling, by means of surface measurement is now made possible with the help of advanced flow monitoring sensors installed strategically on the drilling rig mud returns flow-line. These flow sensors operate with high sensitivity and accuracy, which aid in detecting micro-losses of the drilling fluid; that could be identified as open fractures, micro-fractures or permeable intervals.

By applying an interpretational model in this case study, we were able to infer three different types of fractures, occurring with different apertures and densities. This interpretation was further enhanced by correlating the real-time drilling parameter variations to lithology, advanced mud-gas analysis and X-ray fluorescence (XRF) analysis on drill cuttings in near real-time. The results of this integrated analysis acquired while drilling, showed good correlation with the interpreted fractures from open-hole image logs.

The case study explains the details of the integrated analysis and the relationships observed between various data sets collected while drilling. A localized interpretation model can be generated which could be utilized for reservoir characterization and completions optimization. The objective of this technique is to obtain a fracture analysis data set at a fraction of the typical well AFE.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018