Abstract
The development of offshore heavy oil is sensitive and complex, which is limited by factors such as platform space, economy, pollution and security, so conventional thermal recovery techniques such as cyclic steam stimulation and steam flooding have difficulty in achieving favorable development effect for offshore heavy oil reservoirs. Horizontal-well multi-thermal fluid stimulation (HW-MTFS) process is a relatively new thermal recovery technique, which combines the multiple advantages of gas injection, horizontal well and thermal recovery process. In this paper, the HW-MTFS physical model was firstly designed. Thereafter, the influences of different factors on steam absorption along horizontal wellbore were studied by sand-packed model experiments. Finally, the development performance of horizontal-well cyclic steam stimulation (HW-CSS) process and horizontal-well multi-thermal fluid stimulation process was compared by two groups of physical experiments. The results indicate that different injection factors significantly influenced the steam absorption along horizontal wellbore. Compared with steam injection, the multi-thermal fluid injection could effectively improve the steam absorption along horizontal wellbore. The HW-MTFS process had a higher oil rate and production, and the recovery of HW-MTFS process was 42% higher than that of HW-CSS in three cycles.
Highlights
With the development of global economy and the exhaustion of onshore oil and gas resources, offshore oil and gas resources have recently attracted more and more attention (Sheikholeslami et al 2017; Sheikholeslami and Rokni 2017; Sheikholeslami and Shehzad 2017)
The results indicated that gas–steam injection was a promising technique and gas–steam ratio was a significant factor on the heavy oil recovery
The results indicated that injected CO2 had dual effect of noncondensable gas and solvent during SAGD process in extra-heavy oil reservoirs, C O2 injection improved the volume of steam chamber, and increased the oil rate
Summary
With the development of global economy and the exhaustion of onshore oil and gas resources, offshore oil and gas resources have recently attracted more and more attention (Sheikholeslami et al 2017; Sheikholeslami and Rokni 2017; Sheikholeslami and Shehzad 2017). The results indicated that injected CO2 had dual effect of noncondensable gas and solvent during SAGD process in extra-heavy oil reservoirs, C O2 injection improved the volume of steam chamber, and increased the oil rate. Wang et al indicated that the addition of flue gas to steam could significantly improve the development performance of heavy oil compared with steam-alone injection (Wang et al 2017b). Srivastava et al carried out PVT tests and coreflood experiments to assess the suitability and effectiveness of three injection gases which included a flue gas (15 mol% CO2 in N2), a produced gas (15 mol% C O2 in C H4) and pure CO2 for developing Senlac heavy oil. All the study results could provide theoretical support for the thermal recovery in offshore heavy oil reservoirs
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