New Research and Application of High Efficient Development Technology for Offshore Heavy Oil in China

Abstract

China Offshore oilfield is rich in heavy oil, M oilfield in Bohai Bay is themost thick heavy oil field in offshore by far with the formation oil viscosityas high as 450 ~ 950mPa.s. Using conventional oil field development (depletionand water flooding), the heavy oil field exposed its limits, such as lowproductivity of single well, low production rate and low predictedrecovery. As we all know, the development effect of thermal recovery is not only relatedwith the thermal recovery methods (steam stimulation, steam flooding, etc.), but also related with the thermal medium (steam, hot water, flue gas etc.). Anew thermal media called multi-thermal fluid, which contains steam, hot waterand flue gas was researched for horizontal well stimulation, which is to injectN2 and CO2 at the same time when injecting steam. This multi-thermal fluidcould employ various mechanisms of each fluid, including reducing oil viscosityby heating and dissolving gas, increasing pressure by injecting gas, expandingheating range, reducing heat loss and gas assisting gravity drive etc. With theadvantages of single thermal injection, this method made up the disadvantagesof single thermal fluid injection and can improve steam stimulation effect insome special formation conditions. In this article, the author first analyzed the characterization ofmulti-thermal fluid, and then researched its stimulation theory. Based on thistheory, the single element of geological data, such as dip angle, permeability, rock compression coefficient, formation thickness, oil viscosity, and injectiondata, such as injection volume, gas-water-ratio and CO2 concentration wasanalyzed using numerical simulation software. Based on this result, selectingdata that make more contribution in incremental oil, production rate, and EORto make sensitivity study to summarize formation that multi-thermal fluid couldbe applied.

Feasibility of the Steam-Assisted-Gravity-Drainage Process in Offshore Heavy Oil Reservoirs with Bottom Water

“…It has been steamed 325 wells with 860 cycles. In 2010, a multi-thermal fluid stimulation process is conducted in NB35-2S block in Bohai offshore oilfield [10][11][12][13]. The oil viscosity at the reservoir conditions is about 450~950 cp.…”

Multi-thermal fluid assisted gravity drainage process: A new improved-oil-recovery technique for thick heavy oil reservoir

“…Third, the steam fraction in multi-thermal fluid is always the superheated steam. It has higher enthalpy than the conventional saturated steam Liu et al, 2012;Dong et al, 2014).…”

Roles of Flue Gas in Promoting Steam Flow and Heat Transfer in Multithermal Fluid Flooding

“…At present, the multithermal fluid technology has been applied in oilfield. In Bohai Oilfield, China, due to the limitation of the offshore platform area, the conventional technology based on steam injection is unsuitable and the multithermal fluid technology was introduced [11][12][13]. The field results show high oil recovery and good economic benefit.…”