ABSTRACT
With so many horizontal wells drilled in shale formations, each with as many as 100 fractures, most exploration and development today would benefit from optimizing well and fracture placement. Most agree that a high Young's modulus and low Poisson's ratio indicate a promising shale, but few agree on the exact limits of each value. A few authors have made an acceptable definition of the brittleness index. A key missing component in fracturing practice is a method to automate the placement design of fractures and wells in the most productive segments in shale reservoirs.
In this chapter, a newly developed optimization technique is presented and tested. In this technique, wells are placed in the most productive segments of the reservoir. Fractures are placed in an overlapping or staggered design to reduce the stress-shadowing effect and thus obtain optimal fracture geometry and improve the overall expected reservoir production. The developed optimization technique considers the possibility of staggered fractures, distance between fractures, and well spacing and orientation. This technique allows both for the design of fracture placement and for the sequence of fracturing operations (rank). It is important to note that the optimum distance between fractures is usually not uniform.
The mathematical optimization method developed in this chapter simultaneously optimizes: (1) well placement for fracture development and (2) fracture placement to maximize hydrocarbon production. Well placement has been addressed in existing research, but optimal fracture placement is a novel contribution.
Results from the newly developed approach are compared with the standard approach of uniformly spaced wells and fractures. The comparison clearly shows the advantages of the proposed optimization technique for designing the placement of wells and fractures and determining the sequence of fracture creation.
