Targeted Completions Change Economics in Unconventional Reservoirs
Authors: Smith Charles H. , Menendez Eliud 
Published: March 2015

One of the greatest challenges in any horizontal completion is the need to have efficient completion techniques that will minimize the cost of the completion. Traditional techniques that only rely on systematic perforation and fracture treating techniques do not allow the operator to accomplish any understanding of the problems involved in these completions. Horizontal completions are achieved by perforating at periodic intervals and applying the same fracture treatment to each one of the perforated segments of the well.

Data techniques that apply to conventional reservoirs have historically been perceived as not useful in unconventional reservoirs. Conventional calculations or measurements of permeability, porosity, and rock strength do not necessarily have equivalence in unconventional reservoirs. These important parameters concerning the reservoir are still important but are not as readily understood or measured like conventional reservoirs. Consequently, another data technique must be used.

Recent work has demonstrated the ability of NMR logs to deliver permeability estimates in unconventional reservoirs. Understanding this reservoir characteristic in vertical pilot holes and applying that understanding to the horizontal component of the well establishes the best portion of the reservoir for the horizontal component. In addition, rock mechanics derived from dipole sonic devices have established rock mechanical properties in both the vertical and horizontal directions. This data can also be applied to determine the optimal horizontal landing point for the well in question.

The dipole sonic can establish rock mechanical properties throughout the length of the horizontal section. This data can be used to determine the fracture-treatment characteristics of the horizontal wellbore at any point in its length, thus enabling the most efficient completion for the well.

This paper demonstrates the application of these techniques to derive and establish the best landing point for the horizontal well as well as to establish the most effective portion of the well for perforation and treatment. The ability of the fracture to maintain its shape and size is maximized through this process, which changes the economics of the well.

Introduction

Unconventional reservoirs present difficult challenges to the geologist, the completion engineer, and the production engineer involved. These rocks present a different log response than conventional formations. Standard log-interpretation techniques do not work in the evaluation of the data. The basic geologic task of delineating the reservoir is a fairly simple task, but the fact that the location can be defined does not bring a guarantee in efficient completions. The character of log signature in poor parts of the unconventional reservoir does not distinguish itself in any repeatable manner from the response in the best parts of that same reservoir. Measurements that rely on introducing stimulus to the rock then deducing the character of a producing reservoir are exposed as simply algorithms that may or may not be a good characterization of critical properties required for a good completion.