Observation Lateral Project: Direct Measurement of Far-Field Drainage in the Bakken

Abstract

In 2019, the operator embarked on a very ambitious data acquisition project in the Bakken, 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 (TF) formation instrumented with cemented pressure gauges and fiber optics 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 MB wells was instrumented with fiber optics for cluster-level completion measurements and “frac hit” detection, while the other offset MB well was used to deploy geophones for microseismic mapping. Three different fracture treatment designs were evaluated, with the goal of understanding how fluid volume and rheology, proppant volume and size, and proppant/fluid ratio affect fracture geometry and drainage. Quantitative application of oil and water tracers was used to evaluate the productivity of each treatment design. During the completions of the first three wells, microseismic data provided important measurements to characterize fracture geometry and “offset well” fiber provided strain data to evaluate fracture morphology (i.e., far-field fracture behavior). Stress shadowing was evaluated by combining the microseismic and strain data. These measurements were used to calibrate a hydraulic fracture model to enable more reliable predictions of fracture geometry and morphology. Cluster-level measurements of fluid distribution provided data to support increasing clusters per stage and decreasing stage count. Production has been monitored continuously for more than 12 months, including interference testing to evaluate connectivity. The pressure gauges placed along the observation lateral provided one of the first-ever measurements of far-field drainage as a function of fracture treatment design (450 ft in between two producing wells with 900 ft well spacing). The results show that MB wells can drain the TF at distances of 450 ft, and fracture treatment design can significantly impact drainage and productivity. Although the evaluation, modeling, and trials are ongoing, these results may add significant value by enabling Bakken development with fewer, more productive wells in some portions of the basin.

Experimental Investigation of Low-Frequency Distributed Acoustic Sensor Responses to Two Parallel Propagating Fractures

“…During fracture opening, there is a consistent area of extension, and upon fracture closure, the polarity of the strain response at the fracture plane flips from extension (red) to compression (blue) as shown in Figure 2. To understand subsurface conditions with multiple propagating fractures, a laboratoryscale hydraulic fracture experiment was conducted using an established workflow [1]. The previous work consisted of laboratory experiments simulating single orthogonal fracture propagation in a linear elastic medium (epoxy) with embedded fiber optic cables measuring strain.…”

“…Table 1. Zero-strain curve fit coefficients [1]. The model result estimates the distance from the monitoring well to the fracture front, d f , which is dependent on the lateral and vertical offset between the fiber and monitor well, ∆l and ∆h, respectively, and R D .…”

“…A fiber optic sensor is installed on the monitoring well. When fractures approach the monitoring well, the stress/strain field surrounding the fractures varies [ 1 , 2 , 3 , 4 ]. This change can be registered by the fiber optic sensor through low-frequency distributed acoustic sensing (LF-DAS).…”

“…To understand subsurface conditions with multiple propagating fractures, a laboratory-scale hydraulic fracture experiment was conducted using an established workflow [ 1 ]. The previous work consisted of laboratory experiments simulating single orthogonal fracture propagation in a linear elastic medium (epoxy) with embedded fiber optic cables measuring strain.…”

A new method for interpreting well-to-well interference tests and quantifying the magnitude of production impact: theory and applications in a multi-basin case study

“…However, it is not easy to measure the size and shape of the drainage volume around a well. Proppant settling and fracture roughness prevent proppant from being placed along the full length of hydraulic fractures (Almasoodi et al 2020;Cipolla et al 2022;McClure et al 2022b). Diagnostics such as microseismic and offset fiber can measure the full wetted length of fractures, but diagnostics to measure propped length are not readily available.…”