There is abundant heavy oil resource in Bohai Oilfield and steam stimulation has proven an effective method through several field pilots. Till now, all steam stimulation is conducted by two-trips string for steam injection and oil production individually. That is, when the process of steam injection, soaking and blowout is finished, an oil production string will replace the downhole string through workover operation. According to statistics, the operating charge in one huff-and-puff cycle is more than 2.5 million Yuan. Besides, workover operation takes more than 26 days and results in about 1000 m3 kill fluid leak, which greatly reduce the thermal recovery effect. Considering the drawbacks of two-trips string technology, a new injection-production integrated technology by jet pump, namely single-trip string realizing steam injection and oil production, is developed, which includes downhole string system and surface technological process system. The downhole string provides passages for steam injection and oil production. The temperature and pressure resistance of string system could reach as high as 350°C and 35MPa, respectively, which can adapt to the high temperature environment during steam injecting. The surface technological process system can separate 279m3/d producing fluid and supercharge the power fluid as high as 25MPa, which meet the needs of thermal well production. The new technology tested in X well. More than 6000 m3 steam with 356°C temperature and 16MPa pressure was injected. The downhole string system and Christmas tree withstood the HTHP test and kept in good condition. During oil production, the surface technological process ran run steadily. The pressure of plunger pump was up to 20MPa and more than 120m3 produced fluids were separated by the separator. Compared with two-trips string technology, the new technology saved 2 million Yuan and 21 operating days. Besides, no kill fluid leaked, which improves thermal recovery effect. This is the first time that injection-production integrated technology for steam stimulation is developed and put into field trial. The favorable application result indicates that this technology will promote the high-efficient exploitation of heavy oil in Bohai Bay.
This paper introduces a new water controlling technology to manage water production and improve production performance in an offshore oilfield in Bohai, China. Q oilfield is a typical heavy oil reservoir, mainly developed by horizontal wells. One of the main challenges for the production is the high water cut. Most of the wells experience water breakthrough within one year after put into production and produce for long time with water cut higher than 90%. Besides, the strong anisotropism of the formation aggravates the water breakthrough and makes water control work more difficult. In 2019, a new combined water control technology was applied to manage water influx in horizontal completions. In this technology, the annulus between the wellbore and the inner ICD (inflow control device) /AICD (Autonomous inflow control device) screen is filled with light-but-hard particles. In this paper, the barrier built by the fine particles is called continuous-packer. The existence of this barrier plays a similar role to mechanical packers between each ICD/AICD screen, thus the axial flow of the produced liquid is prevented in the horizontal section. Besides, the ICD/AICD screen is equipped to limit the liquid inflow of each segment based on the design. The purpose of equalizing production profile of the horizontal section achieves through the cooperation of the continuous-packer and the ICD/AICD screen. Untill now, this new technology has been used in more than 6 wells in Q oilfield, including both producing horizontal wells with high water cut and newly drilled wells. The production results show that the water cut reduces about 10% and the oil production increases for the high water cut well. The water breakthrough time and the water cut increasing rate is slower for the new wells comparing with near wells. The successful application of this technology demonstrates its validity for the offshore heavy-oil reservoir with active bottom water. It also provides a new method for the water controlling work for the offshore wells in Bohai oilfield. A detailed plan has been finished to implement this technology in more wells in 2020.
Deepwater gas fields have high bottom water energy and a high risk of seeing water. Higher requirements are put forward for the water control process to control the water effect. This article is based on the actual background and well design of the X gas field in the South China Sea and on three sets of physical simulation experiments and three sets of numerical simulation experiments. An analysis and comparison of the water control effect of a combination of continuous packer, continuous packer and variable density screen tube, and their adaptability evaluation in deepwater gas reservoirs were performed. The results obtained from the numerical and physical simulations are consistent. The experimental results show that the water control process of a continuous packer is mainly based on the water-seeing and water-blocking ability. It is less capable of extending the time to produce water in the horizontal section. However, its water-blocking ability is strong and is able to seal the water spot quickly. It extends the total production time by 12.29% and increases the total gas production by 5.96%; the combined water control process of the continuous packer and variable density screen tube can effectively play their respective advantages of water control. The combination of the continuous packer and variable density screen tube can effectively be advantageous of their respective water control processes, enabling the gas–water interface to advance in a balanced manner, extending the water-free gas recovery period by 11.61%, extending the total gas production time by 15.76%, and increasing the total gas production volume by 13.75%. Both water control processes have good applicability in deepwater gas fields and have certain sand control capability. It is conducive to the one-time completion operation for the commissioning of deepwater gas fields.
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