Improved Heavy-Oil Recovery by Separated-Zones Horizontal-Well Steam Stimulation

Abstract

Summary Horizontal wells are widely drilled to produce heavy oil because of their large reservoir contact. For example, there are more than 500 horizontal wells operated in cyclic-steam-stimulation (CSS) or steam-assisted gravity-drainage (SAGD) processes in Liaohe oil field. The length of these horizontal wells usually ranges from 100 to 500 m. But it is challenging to recover oil along a horizontal well proportionally by conventional steam-injection processes because of poor steam conformance along the horizontal well, which is derived from reservoir heterogeneity, large horizontal-well length, and steam properties. Field investigation shows that only half of the reservoir along the horizontal well is well steamed and recovered, and that the average ratio of oil production to steam injection (OSR) is less than 0.28. In this paper, a separated-zones steam-injection process is introduced to improve steam conformance along the horizontal well; in this process, in which packers, outlets, pressure-sensitive valves, and ball sealers are involved, steam could be injected to the selected zone, separated dual zones in sequence or at one time, or separated multizones simultaneously. In order to investigate steam conformance along the horizontal well and feasibility of separated-zones steam injection, primary laboratory experiments with a sand-packaged model, numerical simulation, and field testing are carried out. These show that steam injected to separated zones could be regulated with sealed packer(s) based on the principles of steam crossflow and superimposing the effect near the packer; therefore, steam conformance along the horizontal well could be considerably improved by separated-zones steam injection. Field testing of 76 wells stimulated by separated-zones steam injection shows that up to 70% of the reservoir along the horizontal well is well steamed on average, and steam conformance is significantly improved.

Design and Field Evaluation of Tubing Deployed Passive Outflow Control Devices in SAGD Injection Wells

“…These injection strings can be installed parallel to each other or concentric. Well completion configurations involving multiple outflow points (OCDs) in tubing along the horizontal well, such as in Figure 1, are being increasingly used for recent SAGD projects and other recovery processes that use horizontal wells and steam [3,4]. …”

“…A preliminary design is done before warm-up, only incorporating the reservoir data obtained from the geo-model and drilling activities, for general well completion design requirements and 2 Assuming bare carbon steel tubing 3 Only option available within TWBS software ordering of equipment. After warm-up, the thermal transient performance of the well [11] is evaluated and the design is adjusted to modify any early steam chamber growth tendencies that might be against the design objective.…”