Moving From Vision to Reality - Optimal-Value Testing

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 114870, "Moving From Vision to Reality - The State of Optimal-Value Testing," by Hani Elshahawi, SPE, Robert H. Hite, SPE, and Melton P. Hows, SPE, Shell, prepared for the 2008 Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, 20-22 October. The paper has not been peer reviewed. Optimal-value testing (OVT) could replace conventional drillstem tests (DSTs) for in-situ measurement of dynamic reservoir properties such as permeability and drainage volume. OVT is any pressure-transient test in which live hydrocarbons are not produced directly to surface. Although OVT is safer, less costly, and environmentally friendly, the OVT-results quality might be inadequate for some development decisions. The technology is immature, and there are issues to resolve. However, with increasing experience, future value-of-information (VOI) decisions about performing in-situ dynamic measurements will, more often, include OVT. Introduction The focus of this paper is the use of dynamic well testing in exploratory and appraisal wells. Historically, the industry called this testing a DST. This type of test, in which hydrocarbons flow directly to surface while measuring rate and pressure, is a major tool in deciding how to develop a hydrocarbon resource. Cost along with health, safety, and environmental (HSE) concerns encourages seeking better ways of obtaining similar reservoir and fluid data. OVT is any fit-for-purpose well testing with minimal cost and HSE effect in which no significant volume of live hydrocarbons is produced to the surface. Three types of tests are wireline formation tests (WFTs), closed-system tests, and injection tests. Background Any assessment of OVT must include an understanding of resource-development uncertainties and the reliability of the technology. The types of technologies considered for OVT are not new, but certainly are not as mature as conventional DSTs. WFT. These tests are performed by use of an electrically controlled formation-testing and -sampling tool anchored at depth (usually on wireline and in open hole) while reservoir communication is established through one or more probes or packers. Modern WFTs can collect a massive amount of data at multiple depths, helping to quantify changes in rock and fluid properties along the wellbore, to define hydraulic flow units, and to understand reservoir architecture. These tests are used routinely in many applications including pressure and mobility profiling vs. depth, fluid sampling, downhole-fluid analysis, pressure-transient testing, and microfracturing. Wireline testers have reached a maturity level at which their performance often can match that of production tests such as those carried out with a DST.