Steam huff-and-puff pilot has been conducted for 2 horizontal wells in Bohai Oilfield since 2011 with total enhanced production of 14.5×104bbl in comparation with cold production. However, owing to limitations of the platform space and wellbore configuration characteristics, real temperature and pressure parameters for horizontal section of thermal wells haven’t been acquired until the first coiled tubing test be successfully applied in C1h before and after steam injection in its second huff-and-puff cycle.
The primary objective of our work in this paper is to accurately grasp the degree of steam utilization along horizontal section through coiled tubing test. The test consists of four main units, that is, temperature test unit, pressure test unit, water cut unit and data recording and storage unit. Minimized facilities and specific dual sealing structure based on integrated system are designed and optimized with temperature and pressure resistance of 300°C and 21MPa in consideration of the platform space, HTHP working environment and test cost. The test procedure is elaborated in this paper.
One of the test is conducted before steam injection for the purpose of basic thermal field construction, and the other is in the soak stage after steam injection for the analysis of steam absorption profile along horizontal section. Pigging operation is necessarily conducted before the test. The first test results show that both the temperature and pressure distribute uniformly, with the highest temperature of 60°C and highest pressure of 9.69MPa, which could match well with well configuration. The second test results show that temperature rises up along horizontal section from 2000m to 2400m with the highest value of 238.6°C at 2400m as well as the pressure value ranging from 17.23 to 17.37MPa. The steam useage along horizontal section of C1h is relatively balanced and uniform according to the test results, which could be consistent with the real formation permeability distribution with the purpose of providing vertification in numerical model.
This is the first time that coiled tubing test is successfully put into trial for HTHP steam injection wells in offshore heavy oilfield. Test results in this paper could provide a basis for the prediction of uniform steam injection, the estimation of gas channeling location and the implement of profile control process in the next huff-and-puff cycle.