Abstract

In North America, refracturing has been found to be effective in many instances for increasing the longevity of the well production and helping to drill and complete offset wells. Several instances suggest that refracturing by bull-heading is relatively ineffective because fluids and proppants are lost in the pre-existing hydraulic fractures. Refracturing through coiled tubing (CT) provides a large benefit in giving ability to pinpoint the location of the refracturing treatment by creating new perforations using abrasive jetting and using diversion pills for isolating high-permeability clusters. This paper helps elucidate the benefits and production gain when using CT for refracturing jobs.

A case study from the Eagle Ford shale illustrates the impact of CT refracturing applications. When CT was hydraulic fracturing was applied in the first generation of wells with 18 stages, 36% extra production was observed in the first year as compared to the bullheading technique. Simulations based on integrated reservoir and geomechanical earth models, complex hydraulic fracture models, diversion simulation, numerical production simulation and finite element computations enable characterizing the productivity from the CT refrac operations. A comparison is made between the bullheading technique and CT based refracturing jobs. The impact of refracturing using CT on the offset child wells to be drilled and completed is also studied.

The study demonstrates that it is critical to place the perforation locations in areas of undepleted reservoir for successful refracturing. Reservoir simulation results in combination with measurements of fluid flow profile in the wellbore can be used to place new perforations in the right sections. Using the diversion pill was found to be greatly effective in improving the fracturing fluid diversion and stimulating the undrained reservoir. With the refracturing using CT, the child wells show improvement in productivity along with the parent well. Overall, the parent and child well combination shows 23% increase in production after one year of refracturing when compared to no refracturing in the parent wellbore.

The new approach is verified through the application of simulation and modeling to prove the benefit of CT refracturing operations in unconventional reservoirs. By adopting the key learnings and approach followed in this paper, operators can maximize their chances to improve productivity and compare various refracturing scenarios.

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