Utilizing Mini-frac Data to Improve Design And Production
Authors: Hagel M.W. , Meyer B.R. 
Published: March 2010

An extension to the current mini-frac procedure is presented to improve the quality of the analysis. The methodology is based on history matching the pressure response during pumping and closure for the mini-frac treatment. This process couples the traditional mini-frac analysis with a three-dimensional hydraulic fracturing simulator.

The fracture propagation solution for geometry and extension pressure is coupled with the post injection pressure decline analysis. The coupling process reduces the possible number of parameter uncertainties.

The measured fracture extension and decline pressure data is used to establish the appropriate fracture geometry model and to perform parametric studies. Reservoir and fluid parameters are then varied to perform further sensitivity analyses.

Repeating the procedure for a multi-cycle mini-frac operation provides the analyst with an opportunity to refine the parametric analyses and select the most probable set of parameters to optimize the treatment. This results in an improved understanding of hydraulic fracture propagation and formation response, which results in a higher probability for further improving production.

The fracture-pressure analysis and procedures provided in this paper generally follow the theory of mini-frac analysis originally formulated by Nolte(1,2). An important difference, however, is that the pressure-analysis used here couples a mini-frac simulator with a three-dimensional hydraulic fracture simulator to predict fracture propagation and pressure response. The mini-frac simulator is first used for preliminary analysis and quick estimates of parameters prior to performing more rigorous parametric studies with the 3-D fracturing model.

Parametric studies and field case examples are presented to illustrate the improved mini-frac/treatment techniques. Simulated values for permeability and fracture height are then compared to more traditional sources of information from lab analysis and logs.

Introduction

Hydraulic fracturing continues to be a popular initial completion technique for operators in Western Canada. Whether it is employed to bypass drilling damage or to stimulate tighter zones, well owners have come to rely on hydraulic fracture stimulation to provide greater economic returns.

Improved production and economic benefits from hydraulic fracturing have been clearly demonstrated over the years. However, to maximize the economic benefits, the fracture treatment must be optimized to the reservoir. Too often critical parameters in the fracture design are not available prior to initiation of the actual fracture treatment. Time constraints and economics are modern driving forces which expedite the initial completion process. Unfortunately, the result is a lost opportunity to obtain the engineering data required to determine the effectiveness of the completion and capitalize on the ultimate deliverability of the well.

Mini-frac pressure decline analysis as presented by Nolte(1,2) first became popular in the 1980's and is used routinely today. An excellent review and detailed description of the theoretical framework and current application of fracture-pressure analysis is given by Nolte in Reference (4). Here Nolte relates the similarity of pressure-transient analysis in reservoirs to fracture-pressure analysis. Nolte, however, places the current state of fracture-pressure analysis in perspective with the statement: "An important difference, however, is that reservoir pressure analysis has developed into a massive discipline during the past 50 years, while fracturing-pressure analysis is in a relative state of infancy. "