A new methodology to obtain the optimum fracture treatment design for a wide range of reservoir conditions has been developed and successfully implemented. The approach discussed here significantly reduces the time required to evaluate an optimum design and limits the materials considered to only those that are appropriate for the reservoir conditions. These improvements make it an ideal methodology for real-time re-design of fracture treatments after feedback from minifrac data has been implemented.
This innovative fracture design methodology has capability to determine appropriate fracture conductivity and an economic optimum fracture length while reconciling these with actual fracture growth behavior in the reservoir. This new methodology incorporates the following simple, automated steps:
Selection of the most cost-effective - fluid from a large industry fluid library - that meets a minimum apparent viscosity requirement at a specified shear rate and temperature condition, to ensure that proppant is placed within the pay zone
Selection of a proppant - from a large industry library - that provides the required fracture conductivity at the least expensive cost
Determination of the proppant concentration that is required at the wellbore to achieve a user-specified dimensionless conductivity criterion for a range of fracture lengths
Evaluation of economic criteria such as net present value (NPV) and return on investment (ROI) for various different fracture lengths by comparing fracture treatment cost and revenues from production response
Determination of the optimum fracture conductivity profile by ensuring a uniform pressure drop down the fracture. The conductivity is adjusted for potential losses from non-Darcy and multi-phase flow, gel damage, embedment, and other proppant damage effects.
Iteration of a fracture treatment schedule that results in the best fit of the optimum conductivity profile.
The oil and gas industry has been actively seeking methods to optimize processes over the last two decades. In the most recent activity, the drive for optimization has focused on cost reduction to improve the NPV. In the completion of a well, the fracturing process has the potential to add the most value because of the enormous effect it can have on overall economics. Since production pays for the entire cost of the well construction and completion, fracturing efficiency is a key factor in enabling production to meet economic needs.
Another need is also evident in the industry; i.e., how to transfer the knowledge of the aging workforce in our industry to the younger generation in order to prepare them for the next two decades. By developing a computer model that captures the optimization processes that an experienced frac designer would follow to design a fracturing treatment, the developer could facilitate the transfer of this knowledge and equip the new workforce with the tools needed to design an optimized fracturing treatment.
The optimization approach to fracture design given in this paper is novel to our industry in that it approaches the problem from the opposite direction; i.e., the conventional design method is used in most cases. This approach reduces the time to develop an optimized solution and continuously honors the economic drivers to find the treatment that will provide the greatest value for the given reservoir parameters.
