Overcoming the Challenges of Coiled Tubing Access into Multilateral Wells and Applying Advanced Distributed Temperature Sensing Intelligent Algorithms to Map Fluid Movement

Abstract

The stimulation of multilateral wells with Coiled Tubing (CT) has always imposed significant challenges to the oilfield. Starting with lateral's access, extended reach coverage, and finishing off with an adequate stimulation fluid placement to ensure treating all targeted zones. This paper presents an engineering approach that enables access to a multilateral open-hole completion and evaluates fluid placement using the Distributed Temperature Sensing (DTS). The through-tubing multilateral access tool has been designed and deployed on a CT string, including a hybrid fiber optic and an electric cable connected to an intelligent Bottom-Hole Assembly (BHA) with multiple downhole sensors. The casing windows or open-hole junctions can be located with a precise real-time measurement of the differential pressure drop across the two downhole bottom-hole pressure sensors inside and outside the intelligent BHA. Moreover, the casing shoe and windows access will be immediately confirmed with the real-time Casing Collar Locator (CCL) signal loss. In contrast, the junction's access can be established just after a few tens of running footage thanks to the real-time inclination measurement from the accelerometer sub added to the BHA for the first time. The identification of access into the mother-bore was intuitively identified with the immediate loss of CCL signal at a depth of the casing shoe. The window localization was confirmed with a low drop in the downhole differential pressure at the intelligent bottom-hole assembly, which was not noticed at the surface. The deviation survey measured by the accelerometer sub showed a matching signature with the drilling deviation survey for both; the mother-bore and the lateral, which were successfully treated. Acquired DTS profile logs showed thought-provoking outputs. After applying the advanced interpretation algorithms, communication between the lateral and various heterogeneities in the formation was detected. The CT intelligent BHA deployment enabled the real-time downhole measurement of pressure drop, CCL, and inclination, allowing a quick confirmation of each lateral with confidence. It supersedes the previously used techniques by eliminating all limitations related to pressure monitoring at the surface and the requirement to tag different measured depths for each lateral. Various conclusions were driven, which allowed re-building operational procedures to improve the matrix stimulation treatments in offset wells. Several domains were integrated to create a fit-for-purpose solution for a complex operation. Joint efforts including stratigraphy, fluids science, and well intervention technologies could yield a proven algorithm to be applied.