Sub-Surface Driven Completion and Well-Design Changes to Maximize Value in the Marcellus

Abstract

A fundamental conundrum common to Unconventional assets is how to understand the relative contribution of the sub-surface versus the drilling and completion practice to our EUR estimates, given the inter-connectedness of many parameters. It is common sense to expect the completion design to change where there is a significant change in the sub-surface. In reality however, this is difficult to implement because intuitive solutions to optimize the interaction of the wellbore to the sub-surface are often hindered by a requirement for quantitative and statistically valid proof, typically measured in the increase in a production performance metric. To address these technical and cross-discipline integration challenges, a new workflow was derived for the Marcellus in Tioga Co. (PA), but the steps are mostly applicable to all unconventionals. The steps in the workflow, applied somewhat iteratively rather than linearly, are as follows: (1) Normalize flow for the well-bore: use inverse productivity index for pressure and also account for lateral length. (2) Normalize for the sub-surface: gross thickness was used as a proxy for HCIIP. (3) Brainstorm hypotheses that might affect EUR: Use sub-surface, drilling & completions and flowback categories and then consolidate. (4) Scrutinize the very best and very worst wells (from the inverse productivity index) in each thickness area to high-grade the hypotheses (called Outlier Analysis). (5) Create a Framework Map: map out those hypotheses that are supported by Outlier Analysis, and distinguish between changes relating to HCIIP and Access-to-HCIIP. (6) Use dynamic modeling as a sensitivity analysis to quantify potential production changes related to individual sub-surface variables. (7) Use multi-variant analysis as an independent cross-check of those hypotheses that are supported and assess the relative impact in the HCIIP and Access-to-HCIIP parameters with tornado charts. (8) Create a strategy map(s) to enable development and economic decision-making. Attempts at correlating a single parameter with EUR were not fruitful, be it a sub-surface or an engineering parameter. However, the framework map derived from this production-constrained workflow has a fit with >80% wells. Despite multiple completion optimization trials, the primary control on production was concluded to be the sub-surface variability and to address this, six drilling and completion design changes were recommended to maximize value of highly heterogeneous acreage.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015