Liang, Guangyue (Research Institute of Petroleum Exploration and Development, CNPC) | Liu, Shangqi (Research Institute of Petroleum Exploration and Development, CNPC) | Liu, Yang (Research Institute of Petroleum Exploration and Development, CNPC) | Zhou, Jiuning (Research Institute of Petroleum Exploration and Development, CNPC) | Han, Bin (Research Institute of Petroleum Exploration and Development, CNPC) | Bao, Yu (Research Institute of Petroleum Exploration and Development, CNPC) | Huang, Jixin (Research Institute of Petroleum Exploration and Development, CNPC)
The preheating start-up is indispensable before converting to super heavy oil and oil sands SAGD process. It is mainly achieved through steam circulation or stimulation. Either way, the preheating time and steam consumption are usually over 5 months and 30,000 tons, respectively, especially for well pairs in reservoir with bottom transition zone or widely distributed mudstone. Thus, a modified technology about dilation by polymer injection was proposed and demonstrated to improve oil sands SAGD performance.
Based on the data of mini-fracture test, tri-axial test and core test of polymer displacement, the feasibility study of dilation by polymer injection technology to improve SAGD process was conducted. On the basis, the pilot test and follow-up steam circulation process were well-designed and history matched by coupled geomechanical and thermal simulations, considering the mechanisms of polymer adsorption, degradation reaction, shear thinning and residual resistance, etc. Specially, the key to success of dilation by polymer injection technology was also analyzed.
The feasibility study indicates that the vertical dilated zone easily creates and fast start-up process can be achieved under high injection pressure. While the reservoir is first dilated to form a high-porosity and high-permeability conduit connecting the SAGD well pair, the polymer solution is then injected into these newly created pore spaces, yielding a greater range of dilated zone which is more uniform along the horizontal section. The history matching results demonstrate that inter-well porosity and permeability significantly enhance. Compared with adjacent well pairs, thermal and hydraulic connectivity obviously improve, both steam consumption and circulation time reduce nearly by half. Besides, the first year oil rate improves in follow-up SAGD process.
The field experience and findings can help to improve the SAGD performance and economy of super heavy oil and oil sands projects, especially for heterogeneous reservoir with bottom transition zone or widely distributed mudstone.
Bao, Yu (Research Institute of Petroleum Exploration & Development, CNPC) | He, Liangchen (Liaohe Oilfield Company Ltd, Petrochina) | Lv, Xue (Sino-Pipeline International Company Ltd.) | Shen, Yang (Research Institute of Petroleum Exploration & Development, CNPC) | Li, Xingmin (Research Institute of Petroleum Exploration & Development, CNPC) | Liu, Zhangcong (Research Institute of Petroleum Exploration & Development, CNPC) | Yang, Zhaopeng (Research Institute of Petroleum Exploration & Development, CNPC)
The Orinoco heavy oil belt in Venezuela is one of the largest extra-heavy oil resources in the world. It has become a major goal for the unconventional oil exploitation in these years. Now, the most common production method is to use the horizontal well cold production without sand. It is an economic and commercial process, and with the reservoir of this area have high initial gas to oil ratio (GOR), porosity and permeability with unconsolidated sand. However, after several years' production, the oil rate draws down quickly caused by the reservoir pressure drops; the key challenge of cold production is that the recovery factor (RF) tends to be only between 8% and 12%, implying that the majority of the oil remains in the oil formation. It is necessary to develop viable recovery processes as a follow-up process for cold production. Generally, steam based recovery method was widely used as a follow-up process for cold production. In this paper, steam fracturing (dilation) Cyclic Steam Stimulation (CSS) operation and Non steam fracturing (No dilation) CSS operation by using reservoir simulator is examined for a post cold production in extra heavy oil reservoir, in order to analyze the performance of the oil rate, cumulative steam-to-oil ratio (cSOR), steam depletion zone, greenhouse gas emission and some necessary parameters.
The key component of the steam fracturing (dilation) is the ability to inject high temperature and pressure steam into the formation to fracture the reservoir rock which in turn raises the rock permeability and mobilized the oil by lowering the visocisity. To compare the results of the dilation and no dilation CSS operation, this study reveal that due to the steam is injected into the reservoir by using the same cumulative cold water equivalent (CWE), the steam condensate; pressurized by steam vapour, fracture the formation. Dilation operation achieves higher oil rate, lower cSOR. The result also show that fraturing (dilation) of the reservoir during steam injection relieves the pressure which in turn lowers the steam injection pressure below the case where No dilation operation ouccurs.
Liang, Guangyue (Research Institute of Petroleum Exploration and Development, CNPC) | Liu, Shangqi (Research Institute of Petroleum Exploration and Development, CNPC) | Liu, Yang (Research Institute of Petroleum Exploration and Development, CNPC) | Luo, Yanyan (Research Institute of Petroleum Exploration and Development, CNPC) | Han, Bin (Research Institute of Petroleum Exploration and Development, CNPC) | Huang, Jixin (Research Institute of Petroleum Exploration and Development, CNPC) | Bao, Yu (Research Institute of Petroleum Exploration and Development, CNPC)
Steam assisted gravity drainage (SAGD) process is widely used in super heavy oil and oil sands projects. These projects generally have higher steam to oil ratio and poor economy, partly because un-uniform steam chamber along the horizontal section forms and it is hard to adjust, affecting by reservoir heterogeneity including muddy interlayer and thief zones. Therefore, it is desirable to explore realistic and promising technology measures for SAGD projects at low oil price.
In this paper, almost all the technology measures for SAGD projects were extensively and deeply investigated in terms of domestic and foreign reports, literatures and on-site experiences. The available research subjects include Xinjiang Fengcheng and Liaohe super heavy oil projects in China as well as ten oil sands project attached to eight corporations in Canada. Better yet, numerous statistics about technology application are reviewed well-by-well, and field application effects for some technologies were verified by deliberate numerical simulation.
Many realistic and enforceable technology measures were systematically analyzed and recommended. Single or multiple stage dilation start-up process assisted by waste water or polymer injection enhanced start-up process significantly. Infilling well pairs or wedge well, and sidetracking horizontal well or fishbone well effectively tapped the unswept remaining oil by steam. The other technologies further improved steam chamber conformance including non-condensable gas co-injection, ICD/FCD technology, differentiated operating pressure strategy, nitrogen plus dispersant foam profile control and other remedial measures, etc. Besides, the present situation and foreground application were summarized and evaluated for several promising new technologies to be studied such as screening low cost mixed solvent to increase solvent recovery, warm solvent gravity drainage (Nsolv) process and in-situ upgrading process assisted by electrical heater or catalytic modification to reduce the capital cost of surface facility, etc.
The paper contains some previously unpublished data of practical experiences, and the findings of this investigation add to the knowledge base information related to improving the SAGD performance and economy of super heavy oil or oil sands projects.
Given its water consumption and greenhouse gas emissions to the atmosphere, it is critical to optimize the steam injection strategy and steam conformance in steam-based oil sands recovery processes such as cyclic steam stimulation and steam-assisted gravity drainage to minimize the steam-to-oil ratio and maximize the cumulative oil volume produced. Given the heterogeneity of oil sands reservoirs, robust adaptive oil sands processes which respond to the system to continuously shift the operation towards desired operational objectives are desired. This kind of adaptive control can be achieved by proportional-integral-derivative (PID) control. PID automated control is a relatively simple method to control well operations in thermal processes by using observed data already measured in existing steam-based recovery processes. Here, a vertical-horizontal hybrid well configuration within an oil sands reservoir, with reservoir properties previously tuned by a history-match to field data, is operated under PID control to demonstrate that automated control can yield improvements of recovery process performance. Here, the well configuration consists of multiple vertical injectors and a few horizontal producers - early in the process, cyclic steam stimulation is initially done in the vertical wells to establish thermal communication within the reservoir. After sufficient communication is accomplished, the steam is injected into the vertical wells and fluids are produced through the horizontal wells in a steam-assisted gravity drainage mode. Automated control must accomplish thermal communication between the vertical and horizontal wells and thereafter the steam must be controlled to minimize the steam-to-oil ratio and maximize the oil rate. The results demonstrate that PID control can be used to improve the cSOR and volume of oil produced.
With the decline of conventional oil production, developing and producing heavy oil resources efficiently is becoming more important. The Liaohe Heavy Oil Field steam operation is unique - it started with cyclic steam stimulation (CSS) operation that transitioned into a continuous steam-assisted gravity drainage (SAGD) operation. With respect to oil production in China, this field is considered critical for heavy oil production and technology development. Cyclic steam injection was initially done through vertical wells. This had the benefit that it provided a good start-up of depletion chambers in the reservoir. These chambers then grew under gravity drainage after continuous steam injection (through the vertical wells) and continuous production through a set of horizontal wells was started. Controlled and deliberate transition from CSS to a gravity drainage process with the objective of optimizing energy intensity (GJ injected per unit volume oil produced) with control enabled through production and thermocouple data is a smart field operation which we refer to as a Reservoir Production Machine (RPM). In this paper, as a first step to understand the operation and its impact on the reservoir, we have history matched the CSS operation based on the injection and production data from field. The use of vertical steam injection wells (formerly the CSS wells) in combination with horizontal production wells operated in a SAGD mode of operation is explored. The history-matched model can be used to develop automated RPM technologies to optimize not only energy intensity but also emissions intensity.