Efficient and Reliable Multilateral Coiled Tubing Intervention Technique for Acid Stimulation: A Case History in the Middle East

Abstract

In recent years, multilateral wells have become more predominant enabling either improved recovery or injectivity depending on the well type. The process of timely accessing the correct lateral with coiled tubing (CT) is still one of the greatest challenges relative to the well intervention. This paper presents a case history in which a flawless 2.375-in CT intervention was performed to stimulate laterals with a proprietary multilateral entry bottom hole assembly (BHA) that steered the CT efficiently into the laterals. The injector well has a natural and un-natural lateral, both of which required stimulation. A proprietary hydraulic multilateral entry tool was selected for the job which reliably locates and enters multiple lateral junctions in a single run. The special working mechanism of the tool circumvents any need for an electrical control or steering system. Along with this tool, a casing collar locator (CCL) was incorporated into the BHA, powered by a proprietary CT conductor telemetry system. Real time data enabled confirmation relative to access into the correct lateral to save time without the need to tag the bottom. A gamma ray (GR) sub can also be incorporated into the BHA to correlate depth where needed. A major challenge for multilateral intervention is time on location. The multilateral entry tool searches for the lateral by rotating 360° until it reaches the desired kick off angle which is confirmed by a surface pressure indication signifying that the correct lateral has been located. The simple yet effective operational mechanism of the multilateral tool allows each lateral to be found and entered in less than 30 minutes once it is positioned at the window. Depth correlation is confirmed with use of either the CCL or GR subs or a combination of the two and the multilateral entry tool is resettable easily by pressurizing, which enables any number of laterals to be located & stimulated. The job was completed safely as per program with more than 4,000 bbl of acid pumped to stimulate both the laterals. The entire operation was conducted efficiently, flawlessly, and post injectivity results of the stimulation resulted in significant incremental injection drainage capability. This combination of BHA's options and the efficient mechanism of the multilateral entry tool to find and enter multiple laterals quickly and reset without the need to pull out of hole, enables the Operator to intervene in any number of branches of a multilateral well in a timely and efficient manner. This is a very important case history for other complex multilateral wells in the region which could benefit from this technology and approach