Abstract
Unconventional reservoirs are an increasingly important worldwide resource. These reservoirs, generally defined by permeability values lower than 0.1 millidarcy, present today's engineer with unique challenges. To date, there are no available methods for evaluation of unconventional wells with respect to estimated ultimate recoveries (EURs). As a result, the conventional approach has been used resulting in initial well reserve and performance predictions containing large amounts of uncertainty. Ultimately, capital efficiency will suffer through these misinterpretations. A better understanding of completion efficiencies and of a well's performance in these new unconventional frontiers is needed.
This paper will present an optimized EUR prediction procedure for the ultra-low permeability unconventional reservoir. The data from a standard mini-frac test will be analyzed and interpreted to produce the desired results. Illustrated within is the integration of geological data, Mini-Frac test (DFIT) analysis, and logging data to predict EUR's and future performance profiles. The DFIT analysis shows itself to be the most influential in this predictive workflow. One should note that the critical step in the process is proper identification of the reservoirs parameters: initial reservoir pressure, permeability, fracture half-length, and reservoir boundary
A reservoir model was built using the results of the proposed workflow. Through multiple simulations, the model produced well-performance curves and EUR values that were in agreement. This procedure generates more accurate and reliable curves than the conventional decline curve analysis approach and properly applied, will improve individual well performance predictions with additional benefits including optimization of future completion metrics and spacing decisions.
