Abstract
Abstract
The expansion of heavy oil and bitumens production is limited by the lack of advanced upgrading facilities and technology. Surface processing, mainly by delayed coking and some hydroprocessing, is very capital intensive. This cost can be more than that for the reservoir engineering facilities. The THAI process achieves substantial upgrading of heavy crude oil directly in the reservoir, via thermal cracking and associated reaction transformations. It captures the underground upgrading because the horizontal producer well process operates via a ‘short-distance displacement mechanism’, similar to that which occurs in the SAGD process.
The results of a 3-D combustion cell test performed on Wolf Lake heavy oil are presented in the paper. Upgrading commenced as soon as the combustion front became anchored on the horizontal producer well. The produced oil viscosity was dramatically reduced, from 80,000 cSt, down to 50 cSt (average). The corresponding API gravity was increased from 10.1 to 20.4 °API (average). The quality of the produced oil was determined from a number of specific analyses, including TAN, Bromine number, SARA, and also water and gas analyses.
The first field pilot of the THAI process is to be conducted by WHITESANDS INSITU Ltd, the heavy oil division of Petrobank Energy and Resources Ltd., at Christina Lake, Alberta, Canada [1]. The pilot is scheduled to start early in 2006, and if the project is successful, the new THAI technology could revolutionize heavy oil recovery and upgrading.
Introduction
Horizontal well applications for heavy oil recovery achieved varing degrees of initial success, some 20 years ago, mainly with steam drive, cyclic steam injection, and especially SAGD (Steam Assisted Gravity Drainage) developments. However, no horizontal well applications were reported for the in situ combustion (ISC) process, even though it had been much in vogue during the 1980's. Towards the end of this decade, it appeared to many in the industry that ISC was possibly in terminal decline, unless some new developments were forthcoming. Using a horizontal well for the ISC process did not appear to be relevant, perhaps because ISC was viewed as simply being concerned with the propagation of a combustion front from an injection well towards a (vertical) producing well. This arrangement is what is known as ‘long-distance displacement’, and is mainly responsible for many of the problems associated with the conventional ISC operation - severe, uncontrollable gas override, leading to early oxygen breakthrough and, very importantly, the inability to maintain vigorous, high temperature oxidation (HTO), because of reduced air injectivity. The latter was either due reservoir problems, but also, frequently, compressor limitations.