Optimizing Well Test Sequence and Duration Using Real-Time Pressure Transient Analysis (RT-PTA)

Abstract

Both conventional and non-conventional well testing and sampling operations require some form of design a priori. Due to the uncertainties in input parameters during the test design stage, test sequence and duration are mostly adhered to especially when memory gauges are being used. These uncertainties are more pronounced during exploratory or appraisal testing; hence, being able to make adjustments throughout the testing operation can result in significant value creation, particularly when operating in a high cost deep water environment. This paper describes how real time pressure transient analysis (RT-PTA) may be used to optimize test sequence and duration in exploratory well testing and sampling. Two case histories are presented that show the impact and value added by combining real time data acquisition, analysis and decision making in the test procedure. Value is achieved by making informed decisions to redesign the test sequence to better meet test objectives, improved stakeholder communication concerning the reasons for these changes and improvements in contingency planning. It is the authors' hope that these examples will be useful to our peers when engaging in Value of Information (VOI) discussions. Several modes of deployment currently exist for downhole data acquisition and transmission to the surface in real time. Case histories showing results from the application of two of these deployment techniques are presented. While no effort has been made to demonstrate the superiority of one method over another, emphasis has been placed on the impact of enabling real time monitoring and analysis of data acquired during well testing operations. The two methods presented, tubing encapsulated cable (TEC) and an acoustic telemetry system (ATS), were deemed most appropriate for each specific application. The suitability of this approach for conventional and non-conventional well testing and sampling, the ability to adapt this technique to different types of tests and of being able to revise test sequence in real time to more efficiently accomplish a given set of goals makes real-time pressure transient analysis (RT-PTA) very attractive.