Steamflooding with horizontal wells promises to be a highly effective method for recovering heavy oils from shallow, thin formations. As is often the case for poorly consolidated heavy oil formations, sand production could constitute a serious production engineering problem. For horizontal wells, this problem could be exacerbated as the sands/formation fines could settle inside, and choke off sections of a horizontal well completely - leading to loss of production. To alleviate this problem, it is often necessary to case the horizontal wells.
This paper reports results of a series of scaled model steam injection experiments investigating the role of a perforated casing on the recovery performance. Fluid production rate, well pressure drop, cumulative oil recovery and cumulative oil-steam ratio for open and cased horizontal wells are determined and compared to determine the impact of the casing.
It is concluded that a casing, though necessary to control sand production into a horizontal well, could lead 10 lower cumulative oil recovery and lower thermal efficiency for the recovery process. For example. oil recovery and the cumulative oil-steam ratio in the absence of a casing were 49.7% of IOIP and 0.62, respectively. The corresponding values in the presence of a casing were 42.9% and 055, respectively.
With innovations in lateral and horizontal drilling technology, more horizontal wells are being used to recover oil and gas world-wide. It has been widely recognized that the main advantages of horizontal wells over conventional vertical wells include larger reservoir contact area, ability to reduce the effects of gas/water coning, as well as the higher probability to intersect systems of vertical fractures in fractured reservoirs. In thermal recovery applications, horizontal wells - due to their extended contact with the reservoir - promise high production rates and improved steam sweep efficiency. For these reasons, many thermal horizontal well projects have been started up, and field-tested in Alberta and Saskatchewan 1–3. The main production mechanism for the AOSTRA Underground Test Facility (UTF) in Fort McMurray, Alberta is steam-assisted gravity drainage. The pilot has been so successful that an expanded Phase B which involves more and longer horizontal wells is being implemented for commercial operation 1. For Esso Canada Resources Ltd. 's Cold Lake horizontal well project, the first phase of operation involves cyclic steam stimulation of vertical wells to provide steam injectivity. Steam is then injected down these vertical injectors to push oil towards the horizontal producer 2. Scepcre Resources Ltd.'s North Tangleflags, Saskatchewan pilot 3 also utilizes vertical steam injectors to mobilize and displace the heavy oil into a long horizontal producer.
Sand production is perhaps the most widespread and costly production problem associated with many thermal recovery projects. The sand and formation fines could either impair production by choking the wellbore or reduce production by preventing the proper operation of downhole pumping equipment. Also, they will require the replacement of equipment because of erosion damage 4.