Solar enhanced oil recovery, or solar EOR, is a form of thermal enhanced oil recovery (EOR), a technique applied by oil producers to extract more oil from maturing oil fields. Solar EOR uses CSP to use the sun's energy to heat water and generate steam. The steam is injected into an oil reservoir to reduce the viscosity, or thin, heavy crude thus facilitating its flow to the surface. Thermal recovery processes, also known as steam injection, have traditionally burned natural gas to produce steam. Solar EOR is proving to be a viable alternative to gas-fired steam production for the oil industry.
In-situ combustion requires standard field equipment for oil production, but with particular attention to air compression, ignition, well design, completion, and production practices. Air-compression systems are critical to the success of any in-situ combustion field project. Past failures often can be traced to poor compressor design, faulty maintenance, or operating mistakes. See Compressors for a detailed discussion of compressors and sizing considerations. Other discussions are available in Sarathi.
Predicting the production response to in-situ combustion (ISC) has been the topic of various studies. Complete numerical simulation of in-situ combustion is difficult because of the complex reactions and the thin burning front that requires small gridblocks for representation. The easiest method is essentially a tank balance, adapted by Prats. The oil and water produced are given by If the volumes are in acre-ft and the production terms are in bbl, a multiplication factor of 7,758 must be used. The estimate of 40% of the oil produced coming from outside the burned volume is an empirical value based on experience. This is the 0.4 term in Eq. 1. Figure 1, presented by Gates and Ramey, combines laboratory results and field observations from the Belridge in-situ combustion projects.
Many useful and reasonably accurate calculations can be made on in-situ combustion to predict the behavior of a proposed project. This page discusses the calculation process involved with behavior prediction. In-situ combustion prediction calculations will be explained in the following diagrams and example calculations. They start with a very simple heat balance and are then extended to more closely represent what happens in the reservoir. Start by assuming that no combustion data are available to get an initial idea of the feasibility of a project.
In-situ combustion processes are largely a function of oil composition and rock mineralogy. The extent and nature of the chemical reactions between crude oil and injected air, as well as the heat generated, depend on the oil-matrix system. Laboratory studies, using crude and matrix from a prospective in-situ combustion project, should be performed before designing any field operation. The chemical reactions associated with in-situ combustion are complex and numerous. They occur over a broad temperature range.