This paper describes how an operator restored the casing integrity of a nonproducing well to resume offshore drilling operations by installing four 10¾-in. overlapping expandable steel patches. From 2020 to 2022, the operator scheduled a sidetrack drilling program, Māui A Crestal Infill (MACI), from the Māui A offshore platform, located in the Taranaki Basin of New Zealand. The operations included eight wells targeting the remaining unswept zones within the Māui A structure. During a reentry in a plugged and abandoned well, MA-03, a multifinger caliper log and a failed pressure test indicated a casing leak in the 10¾-in. intermediate casing. The log identified severe longitudinal casing wear with some fully penetrating holes. This lack of integrity prevented the scheduled operations from being performed. Several lost circulation material (LCM) and cement squeeze jobs attempted to seal off the leak but were unsuccessful. A service company proposed a mechanical repair solution to cover the long interval with four 13-m- (42.7-ft)-long customized, overlapping patches. Later, a second caliper was run to check if the cement squeeze jobs had reinforced the area for better patch support. Surprisingly, the zone appeared significantly more damaged, with a complete circumferential casing breach. Thus, the planned solution looked very challenging to implement. A video camera run, additional thinking, modeling, and cooperative engineering led to a complete redesign of the solution. The lengths and positions of the patches were changed, and one of the patches was assigned to serve as an inner reinforcement. The team assembled, deployed, and installed the patches in an accelerated mode. In 10 days, the casing integrity was fully restored, enabling the 8½-in. sidetrack hole to be drilled to total depth. This case is a typical example of how industry practices should evolve regarding the management of casing integrity issues. Remedial cement squeezes are often prioritized over mechanical options, even though mechanical options are now adjustable, much quicker to implement, and likely offer greater success rates.

ExxonMobil Cepu Limited (EMCL), as the operator of Banyu Urip field in Cepu Block, Indonesia, observed several oil wells with high Gas Oil Ratio (GOR) after several years of production. Oil production curtailment was expected due to limited surface gas handling capacity. Additional stand-off against reservoir gas cap shall be established by performing top perforation interval shut-off to reduce GOR and maximize oil production. Perforation shut-off became more challenging due to high concentrations of H2S and CO2, relatively high reservoir temperature, long perforation interval, and total losses experience. The remedial solution required a V0 “gas-tight” qualification, live well execution, induced minimum to no formation damage, and provided minimum reduction of tubular Inner Diameter (ID) post remedial work to avoid significant production impact and allow future wireline tools deployment. Considering the high profile of Banyu Urip field, which currently produces ~29% of Indonesia’s oil production, EMCL selected the fit-for-purpose remedial method with the highest probability of success. The hydroformed expandable casing patch (patch) with Corrosion Resistance Alloy (CRA) material and its top-down expansion method was evaluated and selected. The re-designing of inflatable element was performed to improve durability in high temperature and verified by laboratory testing. Patches were installed and overlapped to cover the top perforation interval. Seals on top and bottom of the patch extremities formed V0 “gas-tight” sealing mechanism against the casing. The patches were deployed utilizing a smart coiled tubing. All patches were successfully installed as per plan. The wells were brought online with significantly reduced GOR post patches installation. This was the first installation of the patch utilizing smart coiled tubing and ~90 feet Coiled Tubing (CT) tower in sour wells within any ExxonMobil affiliates. The detailed technical preparation, strong safety culture and leadership as well as relentless learnings application have delivered a successful project to reduce Banyu Urip wells GOR and enable EMCL to maximize oil production.

A prolific gas producer in Sarawak waters was shut-in and idle due to a tubing leak resulting in a significant decline in the total hub production. The well remained idle and required immediate remedial action to meet the contractual sales target. Hence, an expandable tubing patch was proposed to isolate the leak and reactivate the well faster. This paper presents data gathered to identify leak location, tubing patch design, and installation using real-time coil tubing. Several logging surveys were performed to detect leak depth including caliper log, leak detection log (LDL), and downhole camera run; since no pressure build-up was observed post bleed-off tubing and casing, while SCSSV was in closed-state. Running caliper log could not indicate severe metal loss of 7-inch tubing, hypothesizing that the leak could be of a smaller dimension. Therefore, LDL was conducted, indicating temperature gradient and acoustic energy changes at a single depth location of 247 ft.THF, above SCSSV. Utilizing the leak depth marker from acoustic log, a downhole camera was staged to verify geometry of tubing leak. Root cause failure analysis (RCFA) was carried out for this tubing anomaly using diagnostics data to determine the possibility of UHP-17Cr-110 tubing failure. The likelihood of tubing failure is attributed to two main causes namely oxygen corrosion cracking and stress corrosion cracking. Based on RCFA outcome, Hastelloy C276, a nickel-molybdenum-chromium superalloy with the addition of tungsten was selected for the patch material, which is V0 rated, internal gas-tight qualification for temperatures up to 150 degrees Celsius and 5,000 psi. Moreover, this patch material satisfies the well conditions at approximately 20% CO2, 200 ppm H2S, 1000 mg/L salinity, and varying Hg concentrations from 800-2,000 ug/Nm3. The design of patch has been improved by adding AFLAS elastomer for the whole exterior of patch to eliminate contacts between the two metals: reducing the risk of galvanic corrosion. Real-time coiled tubing application was selected for setting the patch to ensure accurate depth-sensing control. Additionally, patch is a rig less intervention technique that will not disrupt the production from the existing wells sharing the same drilling platform. Generally, for high-rate gas wells, economic indicators seem lucrative with tubing patch application, where the payout can be achieved within a month of continuous production. The first step in ensuring the success of tubing patch is by running right diagnostics tools such as leak detection logging and downhole camera run, since multi-finger caliper analysis alone would not locate the leak depth and the leak geometry precisely. Valid design inputs are quintessential for the fitting recommendation of tubing patch design which includes accurate reservoir and fluid properties to ensure sustainability of the expandable tubing patch application.