Rigless Exploration Well Testing Experience in Algeria

Abstract

The need to meet ambitious exploration and production targets has resulted in a rapid increase in drilling activity in Algeria, causing a shortage of drilling rigs in the country. Moreover, drillstem testing of exploration wells was consuming as much rig time as drilling. Consequently, Sonatrach (SH)—Algeria's national oil company—searched alternative strategies to maximize use of the existing rig fleet. One of them was to do well testing without a rig, hence freeing up rig time to accelerate exploration drilling. A rigless well testing candidate was selected for the pilot project, first for Sonatrach, from a seven-well exploration campaign. The objectives of the pilot project were to assess rigless testing viability for exploration wells and enable SH to gain sufficient knowledge, skill, and experience to implement the same strategy in subsequent wells. The project started with the detailed design phase, including preparation of well completion and testing programs for the operations, identifying and sourcing of equipment and material, and applying for permits to operate in a remote location without a rig. The project was implemented and managed by Sonatrach, with Schlumberger providing operations support and well testing services. On completion of the first rigless testing operation, a postmortem was conducted to evaluate project implementation, highlight problem areas, and capture lessons learnt. The results confirmed the rigless well testing option to be technically viable and a practical solution for freeing up rig time, especially in drillstem test (DST) applications involving three or more zones with associated cost savings. The decision was made to continue testing multilayer reservoirs without a drilling rig, taking into consideration the lessons learned from the first operation. A list of recommendations was prepared based on procedures followed during this test, and also serves as a guideline for similar projects. Introduction Algeria is a major oil and gas supplier with about 25 billion barrels of proven oil reserves and the third largest natural gas exporter in the world. Sonatrach currently produces 1.5 million bbl oil per day and 16 bcf gas per day, out of which 6 bcf is exported. However, the country is still considered relatively underexplored 1, with vast potential for further discoveries. In addition, prevailing high oil and gas prices have provided a significant stimulus to increase exploration and development activities in the country. Accordingly, Sonatrach's goal is to increase both oil and gas production, and the company has set ambitious targets, especially for gas exploration. The need to meet these targets has resulted in a rapid increase in drilling activity, which in turn has led to rig shortages. Consequently, it has begun implementing drilling optimization projects and evaluating alternative strategies to optimize the utilization of available rigs. One of the key initiatives, with respect to rig utilization, was the pilot implementation of well testing without the drilling rig, as a means of freeing up rig time.