Experimental study on horizontal-well multi-thermal fluid stimulation process in offshore heavy oil reservoirs
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ORIGINAL PAPER - PRODUCTION ENGINEERING
Experimental study on horizontal‑well multi‑thermal fluid stimulation process in offshore heavy oil reservoirs Yigang Liu1 · Jian Zou1 · Xianghai Meng1 · Fayuan Zhou1 · Hao Liu1 · Qiuxia Wang1 · Zhilin Qi2 · Jie Fan2 Received: 9 August 2019 / Accepted: 25 March 2020 © The Author(s) 2020
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 sandpacked 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. Keywords Offshore heavy oil · Cyclic steam stimulation · Multi-thermal fluid · Thermal recovery · Development performance List of symbols ρ Oil density, kg/m3 g Acceleration of gravity, m/s2 L Length, m w Width, m h Thickness, m Φ Porosity, f So Oil saturation, f K Permeability, μm2 μ Oil viscosity, Pa s α Thermal diffusivity, m2/s γ Apparent velocity, m/s X Steam quality, % Lv Steam latent heat, J/kg
* Jie Fan [email protected] 1
Tianjin Branch of China National Offshore Oil Corporation (CNOOC), Tianjin 300459, China
College of Petroleum Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
2
Cw Specific heat capacity of water, J/(kg K) ΔT Temperature variation, K
Introduction 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). Offshore heavy oil as an important part of offshore resources has played an increasingly important role in industry (Yang et al. 2014). Heavy oil resources are abundant in the Bohai Bay of China which has approximately 2.3 billion tons of heavy oil resources (Gu et al. 2007). For heavy oil, viscosity is the key factor determining
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