Five things you didn’t want to know about hydraulic fractures

Abstract

It is common to envision and design hydraulic fractures as if they were simple, planar features that are relatively consistent in width and durable in their flow capacity. Production forecasting is frequently based on a simplified description of the reservoir as a homogeneous single productive layer. In rare instances the pay intervals may be simulated with as many as a dozen layered strata, but even the most meticulous reservoir engineer may mistakenly assign each layer a highly conductive, durable connection with the wellbore. When analyzing the resulting production data, similar assumptions are made, which can erroneously reinforce these misconceptions. Although our industry has been confronted with photographic evidence from minebacks and core-throughs of actual fractures, we have typically failed to incorporate those complexities and challenges into our design, interpretation, and optimization processes. Similarly, we frequently fail to recognize the challenges of highly laminated and highly compartmentalized reservoirs. In many resource plays, hydraulically stimulated horizontal wells appear to be the only completion technique that can achieve economic production rates from these low permeability reservoirs. However the productivity and ultimate recovery from these horizontal wells will be increasingly reliant on durable hydraulic fractures to contact and drain the hydrocarbons through highly laminated formations for the decades necessary to deplete low permeability reservoirs. Oversimplified models typically result in poorly designed completions and missed opportunities. Frequently, the underperformance of a well will be blamed on “poor reservoir quality” instead of correctly recognizing the inadequacy of our created fractures. This paper will examine five limitations of hydraulic fractures and interpretation techniques, and describe the increases in well productivity that can be achieved when efforts are made to address and compensate for these deficiencies.