There is abundant heavy oil resource in Bohai oilfield, and only limited resource could be exploited with cold production technologies. Though cyclic steam stimulation is one of the most widely used and effective technology for onshore heavy oil exploitation around the world, this thermal method could not be directly applied for offshore oilfield for the limited space, bearing capacity and HSE requirement of the offshore platform.

For improving the offshore heavy oil production, feasibility study of the cyclic Steam stimulation for offshore oilfield was conducted and the relevant equipment was developed. A compact modular steam generator was specially developed for offshore steam injection process. The matching equipment including fuel tank, sea water desalinization and air compressor that could be easily resembled on the platform were developed. From engineering aspects, corrosion prevention, isolation tubing and wellhead were also provided for offshore operation. And the LD Oilfield whose underground oil viscosity is about 2336 mPa.s was selected for field pilot.

For field pilot, two horizontal wells has been implemented. 5 well times steam injection has been carried out since 2014 and the stimulation has entered the third rounds. Till now, the cumulative thermal oil production is about 60 thousand m3. When compared with the clod production, the peak oil production rate is about 5.3 times and cycle oil productivity is about 2 times that of the cold production, the valid time for each cycle is about 280 days. For analyzing the stimulation characteristics, the variation of temperature, pressure and saturation distribution in the near well region, and parameters analysis are conducted by reservoir simulation. The temperature profile test is also carried for analyzing the producing degree of the horizontal section of the thermal wells. The test result shows that the 300m horizontal section of the thermal well is evenly heated and the producing degree is relatively good.

In this paper, engineering design and field test of cyclic steam stimulation in Bohai Oilfield are introduced in detail. The result of field test shows that the steam generator are feasible to operate on offshore platform and the cyclic steam stimulation is practical to enhance offshore heavy oil production.

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