Optimizing Unconventional Completions - An Integrated Approach

Abstract

North American unconventional well completion design has evolved dramatically since 2013 in an effort to keep pace with the productivity gains realized in horizontal drilling. Several trends have emerged during the current industry downturn. Among these trends are a focus on core acreage with higher yield potential, the use of longer laterals, a movement towards higher proppant loading (pounds per linear foot), an increased reliance on plug and perf techniques, and decreased stage length and perforation cluster spacing (increased perf density). As a result associated improvements in well initial production (IP) rates and estimated ultimate recoveries (EUR's) have been highlighted in oil & gas operator's quarterly shareholder's reports during 2015 and early 2016.

Unconventional multi-stage completion designs have also quickly evolved along a path paralleling these trends. Horizontal well IP rates and EUR's have also been enhanced through the adoption of integrated completion designs. Recently introduced geo-engineered completions rely on cross-functional expertise and software to integrate petrophysical, geomechanical, drilling, and production data into a completion design. In cases where geo-engineered designs were used, wells showed improvements in EUR's over those associated with increased lateral lengths, proppant loading and stage counts. In one recent case using a geo-engineered design it was demonstrated that fewer stages and clusters achieved higher production than offset wells while injecting less proppant and fluid; thus achieving lower completion cost.

The use of engineered workflows in tight or unconventional reservoirs is not new. Multiple case histories have been published in recent literature illustrating the use of stress variability/contrast or mechanical specific energy (MSE) to generate brittleness or other fraccability indices to group stages with similar rock characteristics. In contrast to engineered designs, newer geo-engineered designs integrate multiple inputs (attributes) to determine basin and formation-specific weighted algorithms that correlate to stage and cluster production contribution improvement. The geo-engineered approach has proven repeatable and can be accomplished even when key wireline or LWD data is not available.

This paper will document how geo-engineered completion designs evolved from engineered workflows. Multiple inputs (e.g. production, wireline/LWD/mud logs, core analyses, and big data from national and state data bases) can be combined to determine stage length and perforation cluster positioning. Case studies will demonstrate that geo-engineered horizontal completion designs deliver superior well production results when compared to geometric, high-intensity plug & perf designs.