Field Experiences: CO2 HuffnPuff Test at the Minami-Aga Depleted Onshore Oil Field in Japan

Abstract A huff‘n’puff CO2 injection test was conducted in a depleted onshore oil field in Japan. This pilot test was conducted to evaluate the effectiveness of CO2-enhanced oil recovery, assess the technical validity of various monitoring tools used for detecting CO2 behavior in the reservoir, and gain operational experience with CO2 injection. The pilot test was conducted in a newly drilled well. Extensive geological information, including wireline logging and core sample acquisition, was collected before the pilot test and used to characterize the pilot test area and design the test procedures. Approximately 100 tons of high-purity CO2 purchased from industry was transported to the site via trucks and injected into the newly drilled test well. CO2 injection last two days, during which a pump and heater at the site were used to maintain CO2 in a dense liquid phase at the well-head condition. The well was then left to a soaking period for 23 days before being brought back into production for 5 days. A clear increase in oil production rate was observed after CO2 injection. In addition, a production logging tool and a pulsed neutron reservoir saturation tool revealed the CO2 flow paths and areas of residual oil remobilization. This study presents the pilot test results, including the injection and production profiles, in situ CO2 monitoring with wireline tools, and evaluation of well deliverability based on pressure transient analysis at each test sequence.