Breathing new life into postmortem analysis: the testing and formalization of a methodology for the identification of key failure modes in dry holes

Abstract

The petroleum exploration industry relies on various subsurface data and interpretations to minimize risk and uncertainties and maximize gains. Dry holes provide a wealth of useful subsurface information. However, far too often a company drills a dry hole and either does not conduct a postdrill analysis (postmortem), or incorrectly determines the failure mode. The purpose of this study is to formalize and test the applicability of a postdrill methodology (a decision tree) that helps identify the main failure mode for dry segments tested by conventional wells. Use of this decision tree allows the interpreter to evaluate and identify specific failure modes such as reservoir presence, reservoir deliverability, structure, seal, source maturity, and migration. The decision tree was tested on three exploration wells drilled in the Taranaki Basin, offshore New Zealand. Each segment’s key failure mode was identified based on the comprehensive, integrated evaluation of both pre- and postdrill reports, seismic data, well logs, geochemical analysis of gases and source rocks, and other materials freely available through the New Zealand government. Each individual segment’s unique failure mode has been carefully identified and compared to the failure mode(s) presented by the original operator of the well. It is my hope that this decision tree, or its customized versions, will become the best practice in postdrill analysis across the exploration industry. However, the acceptance and utility of the decision tree is tied largely to its applicability and ease of use. With that being said, the methodology described has met all of the objectives of this study’s evaluation, but should continue to be tested on other exploration wells from a variety of sedimentary basins.