Description:
This hydraulic fracturing process, developed by Texas Tech, is a method for enhancing the far field network complexity in subterranean formations by optimizing the placement of fractures along the deviated wellbores.Texas Tech's fracking technique is a modification of the zipper frac that initiates fractures in a staggered pattern. Field tests demonstrate that the modified zipper frac improves the performance of fracturing treatment when compared to the original zipper frac by increasing contact area and eventually enhancing fluid production.
Modified zipper fracking takes advantage of concepts developed in alternating fracturing and zipper frac to create more complexity in the reservoir. Unlike alternating fracturing, modified zipper frac is simple to practice and doesn't need special down hole tools. In this design, fractures are placed in a staggered pattern to take advantage of the presence of a middle fracture for each two consecutive fractures. The risks of stress reversal near the wellbore as well as communication are minimal compared to the other designs. Modified zipper-frac not only shows improvement in fracture complexity from a geomechanical viewpoint, it also shows promise in enhancing long term production of the reservoir from a fluid flow aspect. Modified zipper frac design can potentially increase the stress interference between the fractures and create an effective stimulated reservoir volume to enhance hydrocarbon production.
Optimizing the Placement of Fractures for Improved Complex Network of Fractures
The spacing between fractures has a major impact on the changes in stresses in subterranean rock formations. Conventional fracturing techniques can't create complex fracture networks away from the wellbore. Recently developed techniques are designed to overcome this problem. However, those techniques are operationally difficult to perform. Researchers atTexas Tech Department of Petroleum Engineering have produced results that give valuable insight into the interpretation of microseisms and illustrate various optimized designs of hydraulic fractures in horizontal wellbores.
Similar to zipper fracking, the modified zipper frac can be applied in multilateral completions where two or more laterals will be fractured to create a complex fracture network. The domination of stress perturbation in zipper frac design is limited to the area near the tips, while, with the modified zipper frac, the area between fractures will be altered by stress interference caused by the middle fracture initiated from the other lateral.
Publications:
Hydraulic Fracturing Design and Optimization: A Modification to Zipper Frac, SPE Annual Technical Conference, October 2012