_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 226370, “Case Study: Successful TCP and Acidizing Operation Into Depleted Gas Reservoir for CCUS Project, ” by Shun Dotoku, SPE, Ayumi Kubota, and Miki Kohyama, INPEX, et al. The paper has not been peer-reviewed. _ The Hirai onshore gas field in Japan was selected for CO2 storage. Its highly depleted condition after historical hydrocarbon production and its highly heterogeneous quality posed technical challenges for the completion work of wells in the field. This paper presents a case study of oriented tubing-conveyed perforation (TCP) followed by acidizing operations. Introduction A blue hydrogen and ammonia production and usage demonstration project in Kashiwazaki is the first example in Japan of implementing an integrated process from production to the utilization of hydrogen and ammonia. The natural gas produced from the Minami-Nagaoka gas field will be used as feed gas, and CO2 emitted during hydrogen-plant production will be injected into the Hirai gas field. Gas production from the Hirai field began in 1970, ceasing in 2014 because of depletion of reservoir pressure and the encroachment of water into production wells. Current reservoir pressure is lower than hydrostatic pressure. The target reservoir of the gas field is composed of volcanic rocks, which have high heterogeneity with a wide range of permeability observed in nearby existing wells. For carbon capture, utilization, and storage (CCUS) operations, three wells were drilled: a CO2-injection well, an observation well, and a production well, respectively. The production well will be used in case sufficient production potential is confirmed from an enhanced gas-recovery effect. All three wells were planned to feature distributed acoustic sensing (DAS), distributed temperature sensing (DTS), and distributed strain sensing (DSS) fiber-optic cable along the production casing up to perforation depths and permanent downhole gauges (PDHGs) as a part of the CCUS monitoring plan. This paper focuses on the operation results of the production well, which was the first of the three wells drilled. Methodology A TCP shoot-and-pull option, followed by acidizing, was adopted for perforation operations because of the following identified benefits: - A casing-and-perforation option was required to install fiber-optic cable along the casing and to prevent injected CO2 leakage. Production casing was installed with fiber-optic cable. - TCP, rather than wireline perforation, was adopted to aim for longer perforation intervals to overcome the heterogeneity of rock quality and provide enough perforation penetration depth, which had to be deeper than the mud-invasion depth. - PDHG subsurface cable and a control line for the surface-control subsurface safety valve were installed in the completion string. Oriented perforation was required to adjust the orientation of the gun away from the fiber-optic cable along the production casing. - As well as mud loss during drilling operations, mud loss after use of the TCP gun also was a major concern because of static overbalanced conditions, even with dynamic underbalanced perforation. To prevent mud loss during TCP operations, spotting with calcium carbonate (CaCO3) was planned through the circulation sub in the TCP string immediately before gun use to minimize mud-loss volume and proceed with the completion operation. - An appropriate acid recipe was selected for an acid-treatment job to dissolve CaCO3 without causing corrosion problems in the tubulars.
Chris Carpenter (Mon,) studied this question.