this article begins on the next page F F JCPT82-01-03 HEAVY OIL The use of solvents and gases with steam in the recovery of bitumen from oil sands D.A. REDFORD Alberta Research Council Edmonton, Alberta ABSTRACT The use of the C02, ethane andlor naphtha together with steam was investigated as a means of improving recovery and other operatilig parameters in the interwell vertical steam-stimulation process for recovery of bitumen from oil sands. A total of sixty-three experiments were conducted using a two-well, 45-cm-diameter, three-dimensional elemental physical simulator operating at an overburden pressure of 3.5 MPa. The results of twenty of these experiments arepresented.By examining the results, the major mechanisms by which recovery occurs were determined and the impact that these mechanisms would have on field operations are discussed. Introduction The Athabasca deposit of the Alberta Oil Sands is one of the major petroleum deposits of the world. Its high viscosity (5,000,000 cps at reservoir conditions) and high bitumen saturation and hence low injectivity, however, provide some unique recovery problems. Because of its high viscosity, the bitumen has no mobility and cannot be moved forward by an advancing front; because of its high bitumen saturation, there is limited access to the deposit to enable the entry of agents such as heat, solvents, gases, surfactants and bacteria which D.A. Redford David A. Redford is a senior research officer with the Alberta Research Council. Over the past twelve years, he has worked on contract research for a number of oil companies, developing recovery methods for Alberta oil sands. His research has concentrated on thermal recovery methods and, in particular, all aspects of the use of steam, including: well completion, physical and numerical simulation for evaluation of recovery processes and parameter development.Dr. Redford is currently contract coordinator and engineering manager of the Oil Sands Research Department of the Alberta Research Council. His BSc in chemical engineering and his PhD in physical organic chemistry were both obtained from the University of Saskatchewan. Montreal _ could alter the viscosity of the bitumen. The Alberta Research Council has developed a process whereby access to the deposit is initially achieved by using hydraulic fracturing or horizontal boreholes near the base of the deposit. These initial communications are then expanded to provide a hot communications path between injectors and producers. A cyclic process is then initiated involving pressure build-up and depletion cycles, whereby the heated front is forced to progressively move up the formation, thereby achieving bitumen recovery. The process has been termed in-terwell vertical steam stimulation.In earlier work reported by Redford and McKay(l), it was shown that the process, when operating at 2.1 MPa, was substantially improved by the addition of hydrocarbons to the steam. This work has now been extended to the study Of C02 and ethane, t'ie combination Of C02 and hydrocarbons, and a...

The use of hydrocarbons together with steam was investigated as a means for improving recovery and other operating parameters in the interwell vertical steam-stimulation process for recovery of bitumen from oil sands. A total of 42 experiments were conducted using a two-well, 18-inch diameter, three-dimensional elemental physical simulator operating at conditions close to those anticipated in the oil sands area of interest. The results of 20 of these experiments are presented. A range of hydrocarbons from methane through ethane, propane, butane, pentane, natural gasoline, naphtha, to synthetic GCOS crude were investigated. The results of many of these experiments are presented and a number of observations and presented and a number of observations and conclusions drawn. A proposed recovery process based on this work is presented. Introduction The Athabasca deposit of the Alberta Oil Sands is one of the major petroleum deposits of the world. Its high viscosity (5,000,000 cps at reservoir conditions) and low overburden, however, provide some unique recovery problems. While it would be desirable to use high-temperature, and hence, high-pressure steam to raise the temperature of the reservoir and hence lower the viscosity to an acceptable value, the low overburden places limits on the pressure that may be used. The overburden in the deposit ranges in depth from zero along the Athabasca river valley, to 2,000 feet in the Birch Hills area. About 10% of the deposit has an overburden less than 150 feet and is amenable to strip-mining, while the deeper parts of the deposit can be recovered by use of high-pressure steam or in situ combustion. There is, however, a large in-between zone which is too deep for surface-mining and yet is too shallow to allow the use of high pressure. The Texaco lease, with an overburden of about 300 feet, lies within this zone and the intent of the work presented here was to develop a process suitable for this and like leases. It was known from field experiments conducted by Shell Oil Company in the Muskeg River area, and by Canadian Fina Oil in the Steepbank area of the Athabasca deposit, that the results of the use of steam alone at these shallow depths had not been encouraging. It was also known that low molecular weight hydrocarbons could be used to lower the viscosity of the crude, however, it was generally believed that the use of many of these additives would result in precipitation of asphaltenes from highly asphaltic crudes such as Athabasca bitumen. This work was therefore undertaken to see if a combination of hydrocarbon additives with low-pressure steam could be used to recover bitumen from the oil sands, and what adverse effects might occur. EXPERIMENTAL EQUIPMENT The experiments were conducted in a three-dimensional elemental model referred to as the 18-inch simulator, which has been briefly described elsewhere. The term "elemental model" indicates that the experimental approach is to take an element of the formation and to conduct experiments on that element at conditions comparable to field operating conditions. This type of model is useful for screening a wide variety of recovery processes, but accurate scaling of the experimental results to predictions of field performance requires a complicated mathematical performance requires a complicated mathematical manipulation of the data. (By contrast, the results from a scaled model may be more easily transferred to field performance predictions, but the problem is to design the model in the first place.)

A three-dimensional physical simulator was used to carry out experiments on a variety of novel processes for the in situ recovery of bitumen en from the Athabasca oil sands deposit. Runs were made at up to 500 psi operating pressure. The low temperature oxidation process, comprising combinations of air and steam, was shown on the basis of the laboratory data to be a most promising recovery technique. The paper com-pares the performance of the low temperature oxida-tion process with a straight steam displacement pro-cess and describes the factors which determine the optimum performance and the mechanisms which are believed to contribute to the effectiveness of the process. INTRODUCTION There is a growing recognition of the role which the Alberta oil sa nds deposits could play in providing for Canada's future energy needs. Research and de-velol)ment of processes for the in situ recovery of bitumen have been correspondingly accelerated, and many organizations are involved in the effort at both the laboratory and field level. The main thrust of this research has undoubtedly been to adapt thermal recov-ery processes which have been operated with varying degrees of success in heavy oil reservoirs in the United States, Venezuela, and elsewhere. The most promising processes for the Alberta oil sands are generally con-sidered to be steam drive, steam stimulation and wet combustion. Of course, the possibility of more exotic recovery processes, such as those discussed by Flock and Tharin,"I being brought to eventual commercial fulfillment, should also be considered. Nevertheless, the consensus would probably be that the first com-mercial in situ recovery scheme will be based on known thermal re(@overy technology. The special proble ms posed by the Alberta deposits, when compared with heavy oil reservoirs elsewhere, are well-known and have been thoroughly discussed by several authors.1','@ll It appears likely that the known processes will need at the very least to operate at their full potential and, more probably, require improvement.Texaco Exploration Canada Ltd. has been actively involv,d sir).ce 1971 in the development of a commer-cially viable in situ recovery process for the Athabasca deposit, through its I)ilot project located some 12 miles south-east of Fort MeMurray, and through an inten-sive research program carried out under contract by the Alberta Research Council. Results from the field pr,gr,, have been sufficiently encouraging to war-rant an expansion of the number of wells and of the pilot facilities, which was undertaken in 1975-76.The laboratory program has involved an extensive investigation of a variety of in situ recovery processes for the Athabasca deposit. Much of the eff ort in this program bas been devoted to the development of im-provements to the steam drive process. In this paper we present the results of experiments involving the simultaneous injection of non-condensible gases and steam. Of the gases studied, air showed the most promise of being an additive which could markedly enhance th(@ rec...

Despite 60 years of effort, the Athabasca oil sands deposit, the largest of the Canadian oil sand deposits, is the only deposit for which a promising in-situ recovery process has not been developed. This paper reviews the many field pilots which have been attempted in this deposit, plus a number of pertinent Plots from related deposits. It then reviews the recovery processes put forward by a number of authors and sums up our current knowledge of this immense untapped Canadian resource and the state of our technology as related to its recovery. With this background in mind, the author gives his views on the state of the technology and indicates the most promising recovery pro-cessesfor a number of different geological conditionsfound in the Athabasca deposit. The author concludes with a review Of some of the key problem areas where progress must be made 'f commercial recovery is to occur. Introduction In 1930, Absher(l) wrote to his shareholders "I feel that we have overcome the technical difficulties and are able to pro-duce (the Athabasca deposit) on a commercial basis". Absher was the first to attempt to recover oil from the Athabasca bituminous sands by in-situ means. In the sixty years since his attempts and despite Absher's confidence to his shareholders and numerous subsequent attempts by others, the Athabasca deposit remains a formidable challenge. While commercial ex-ploitation is occurring from the shallower parts of the deposit by surface mining, and promising in-situ methods have been developed for the Cold Lake and Peace River oil sands deposit and for the Grosmont carbonate deposits, the 90% of the Athabasca deposit which is too deep for surface mining still remains a tempting motherlode just beyond our reach.This paper reviews the many field attempts which have been tried and some of the concepts which have been considered to unlock this immense resource. It also comments on our ex-perience to date and indicates the author's views on some of Keywords: Oil sands, In-situ recovery, Steam injection, Steam stimulation, Fracture pressure, Steam drag, HAS drive, Gravity drainage, Ablation process. Paper reviewed and accepted for publication by the Editorial 52 the more promising technologies which warrant further _ testing. Review of Athabasca Field Tests The Bituminous Sand Extraction CO-LiMited During the period 1926 to 1931, Absher as the principal engineer for the Bituminous Sand Extraction Co-Limited, attempted in-situ recovery from the Athabasca deposit. His early work using steam and superheated steam was at very shallow depth (10 m to 15 m), but in 1926, he sank several wells to a depth of 100 m (overburden 55 m), and produced some bitumen using superheated steam. The following year, and for the next few years, more wells were completed in the area and a i ype of downhole steam generator or in-situ com-bustion was'employed, however, no attempt was made to drive between wells, but rather to produce back to another part of the same well. Although some bitumen was produced and Absher was enthusiastic...

The Underground Test Facility is designed to test the application of the steam-assisted gravity drainage process for the in situ recovery of bitumen, using horizontal wells drilled from tunnels below the pay zone.