Investigation of effects of swelling on wellbore stability in Barnett Shale oil reservoir
Alwesaibey, Mohammed A.
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Oil and Gas companies want to test shale swelling to maintain wellbore stability while drilling in shale-oil wells. Wellbore instability especially in unconventional reservoirs has been increasingly studied by oil and gas companies to reduce non-productive time and cost. Some of these problems are poor hole cleaning, sidetracking, stuck bottom hole assembly (BHA), fishing and lost circulation. The industry has spent a lot of many to try to solve these problems in shale formations. To improve drilling in shale formations and reduce their swelling, we need to study and understand their properties. Several studies on shale swelling reveal that swelling is a major problem and a complicated matter for drilling engineers who daily deal with wellbore instability problems. Many experiments have been performed on common shale samples, which are different from shale oil samples. In this study, we selected core samples from Barnett shale formation to investigate swelling properties in the laboratory. The swelling tests were conducted on six core samples half submerged in two different drilling fluids which are Oil-Based mud and 7% KCl. Six experiments have been conducted using strain gages to measure the axial and lateral swelling in submerged and non-submerged areas. The experiments have shown that the maximum and minimum swelling occur parallel and perpendicular to the bedding planes, respectively. Therefore, drilling perpendicular to the bedding provide a more stable wellbore in terms of swelling. The OBM results show 90% less swelling compared to the 7% KCl results. Thus, using OBM as a drilling fluid in Barnett shale formation would cause less wellbore stability problems in matters of swelling.