Benefits of Engineering Fracture Design. Lessons Learned from Underperformers in the Midland Basin.

Abstract

Hydraulic fracturing (HF) is a very complex engineering process. It involves rock and fluid mechanics, mixed mode rock failure and transportation of individual proppant particles. This process is multiscale both in time and spatial domains that is why it is almost impossible to create a fully coupled 3D model with a detailed description of physical and chemical processes even with significant assumptions. Recent data indicates well completion becomes more expensive than the drilling itself for several unconventional reservoirs. The reason is an increase of fluid and proppant pumped at high rates. Thus, the critical importance of engineering optimization of fracture spacing and individual pumping schedule for maximization of Net Present Value (NPV), Estimated Ultimate Recovery (EUR), and other metrics in the "lower for longer" price environment. Unfortunately, unconventional operators see little value in fracture modeling because of its complexity and amount of data required for any reasonable predictive power. That is why many companies consider geometric design as the cheapest and hence the most efficient option thus resulting in trial and error to optimize HF design. In this paper we use publicly available well logs and completion data covering the Midland Basin from the University Lands website. We also demonstrate that HF model calibration with microseismic data and stochastically generated Discrete Fracture Network (DFN), although is a challenging task, may improve our understanding of fracture design pitfalls and to become an essential step for optimum engineering design. Insights from our work can be useful to increase the predictive power of in-house models and reduce total cost and effort involved in this complex modeling.

Physics-Driven Optimization of Drained Rock Volume for Multistage Fracturing: Field Example from the Wolfcamp Formation, Midland Basin

“…Extensive stress shadowing between the closely spaced fractures lead to individual fractures propagating upward and downward, alternating between stages, leaving significant portions of near-wellbore rock volume unstimulated (Parsegov et al 2018). Separately, a high-resolution study of drainage around individual fractures of a horizontal multi-stage fractured well (only 3.5 miles due south from the stacked wells currently studied) identified the occurrence of stagnation (dead zones) between adjacent fractures, where the drainage is inefficiently slow.…”

“…The present study expands our earlier work on wells in the Wolfcamp Formation, Midland Basin. Previous studies included an analysis of fracture treatment efficiency (Parsegov et al 2018) and the high-resolution visualization of the drained rock volume using flow simulation based on Complex Analysis Methods (Weijermars et al 2017b(Weijermars et al , 2017a. The basic insight from our previous work is as follows.…”

“…Reservoir Geomechanics. Our forward modeling workflow for hydraulic fractures of well 46H is similar to that described in (Parsegov et al 2018). We analyze publicly available logs for the target well 46H as well as for an offset well 31H (wellbores are 500 ft apart) and use regional correlations to construct realistic synthetic logs for the static Poisson's ratio (PR) and Young's Modulus (YMS).…”

“…DFIT or falloff test data may improve our understanding of the closure stress profile. For the sake of brevity, we refer to Parsegov et al (2018) and provide in Fig. 3 only the final results of 1D geomechanical modeling -which identifies the main geomechanical parameters, reservoir properties, and composition at each depth in the reservoir.…”

“…With fracture treatment leaving significant portions of the near-wellbore region unstimulated (Parsegov et al, 2018) and the production flux not draining dead zones between the fractures and between interfering wells Weijermars and Nascentes Alves 2018) there is room for improvement of completion designs. We build forward on previous insights by proposing a practical workflow and by making recommendations for physicsdriven optimization of the rock volume drained by wells with multistage hydraulic fracturing in unconventional reservoirs.…”