Evaluating Stimulation Effectiveness with Permanent Optical Fiber and Sealed Wellbore Pressure Monitoring: Bakken Shale Case Study

Abstract

Summary In 2019, the operator embarked on a data acquisition project in the Bakken, an unconventional shale play in the USA, with the goal of mapping far-field drainage and characterizing completion performance. The project consisted of a six-well pad (10,000-ft laterals) with a dedicated observation lateral located in the Three Forks formation instrumented with cemented pressure gauges and external optical fiber along the 10,000-ft lateral. The observation lateral was offset by Middle Bakken (MB) wells ~450 ft on either side (~900-ft MB-MB well spacing). One of the offset MB wells was instrumented with external optical fiber for cluster-level completion measurements and fracture hit detection. Characterizing hydraulic fracture geometry is critical to improving completion designs and optimizing well spacing. Until recently, microseismic has been the primary diagnostic for estimating “bulk” or stage-level fracture geometry (Warpinski 2009) and parent-child interactions for modern multicluster plug-and-perf completions (Cipolla et al. 2018). However, microseismic cannot provide details on individual fractures or cluster-level measurements. With the continued advances in fiber-optic technologies, we can measure cluster-level fracture behavior at the wellbore and in the far field (Ugueto et al. 2016, 2019). Characterizing the relationship between wellbore and far-field fracture geometry, referred to as fracture morphology, is important when simultaneously optimizing completion design and well spacing. Microseismic and fiber optics are very robust, but expensive, technologies, and this limits the frequency of their application. The recent introduction of sealed wellbore pressure monitoring (SWPM) enables lower-cost, higher-volume data acquisition but may not provide the same level of detail compared with microseismic and fiber-optic measurements. This paper presents a case history that details the application of permanent fiber optics and SWPM to characterize fracture geometry and morphology using distributed acoustic sensing (DAS) for near-wellbore (NWB) measurements along with SWPM and crosswell strain for far-field investigation. This is the first example of both NWB and far-field optical fiber measurements being used to evaluate cluster efficiency in conjunction with SWPM. The SWPM results compared favorably with the fiber measurements; stages with more uniform distribution based on the NWB DAS data also had higher volume to first responses (VFRs) measured using crosswell strain and SWPM.