Enhanced Oil Recovery Production Research Articles

A new approach for ranking enhanced oil recovery methods based on multi-gene genetic programming

Ranking the appropriate enhanced oil recovery (EOR) methods for a specific oil field characteristic is a difficult and challenging task due to the large number of related parameters and financial risks. However, an intelligent ranking tool enables making important decisions about potential EOR strategies by using previous reservoirs experiences. In this research, first, a new production rate consisting of natural production and EOR production called EOR-PR is introduced, which resolves the shortcomings of the proposed rate of previous research. Then, a new machine learning approach for ranking EOR methods based on predicting the EOR-PR values is proposed. In this approach, the efficiency of methods on specific conditions of a reservoir including rock and fluid characteristics is calculated numerically, which is simply comparable. In this regard, Multi-Gene Genetic Programming (MGGP), which is a powerful machine learning method for modeling engineering problems, has been employed to predict EOR-PR values and then its performance has been compared with artificial neural network method. The results show that MGGP with an average of 0.982 for R 2 correlation has a significant performance in this issue. Also, this method, unlike conventional machine learning methods, provides a definite function as the output that allows further analysis for reservoir experts.

En Route: Increasing Recovery Factors: A Necessity

President's column To satisfy the increasing energy needs of the world during the next decades, adding substantial new oil reserves will not be an option, but a necessity. There are different ways to achieve that: Continuation of exploration. Exploration for new resources will continue to play an important role but will become more difficult and will not be sufficient to meet our needs. Development of unconventional oil, like oil sands and oil shales. Unconventionals are quite promising, but production will increase slowly. Improvement of the recovery efficiency of our producing fields. This means producing a fraction of the enormous amount of oil that is currently being left underground. The current ultimate average recovery factor for oil fields, on a worldwide basis, is about 35%. This means that about two-thirds of the oil that has been discovered is left within the reservoir. We have under our feet, in well known locations, enormous prospects for booking new reserves. Increasing the average ultimate recovery factor from 35% to 45% would bring about 1 trillion bbl oil! The questions are how to achieve that goal, and is it realistic? How? Technology will be the key, in many domains: advanced wells with more contact with the reservoir, more efficient lifting systems, devices such as downhole or seafloor separation, better reservoir monitoring and management, and, very importantly, tertiary recovery or enhanced oil recovery (EOR). Is it possible? We know the answer, it’s “yes.” Why? Because this has been done in one place already, Norway. In this country, a continuous policy of incentives for developing and, more importantly, deploying new technology has been in place for the last 30 years. And the overall results are quite impressive. Thanks to many new technologies the average ultimate recovery factor has been increased by more than 10% during this period. I would like to elaborate a little on EOR, as it will certainly play an important role. EOR was promising 30 years ago, but it never developed as well as many people anticipated. However, it is interesting to note that although EOR production is relatively small today, it is still significant—around 3 million B/D. I recently visited the giant Daqing oil field in China. This field is now very mature, with a water cut of more than 90%, but the oil production rate has maintained constant over years thanks to a progressive deployment of polymer flooding, which is now implemented in about one-third of the field. That is an impressive success story and an example for rejuvenation of mature fields. Also, a number of EOR projects have been launched recently. This includes small-scale pilots, but also a lot of large-scale operations.

Cold Production And. Enhanced Oil Recovery

Introduction Economical heavy oil production is possible by allowing formation sand to be produced along with fluid. Cold production has potential to increase subsequent enhanced oil recovery (EOR) efficiency, operating new technological possibilities for continuedeconomical oil production from these reservoirs. Heavy oil (10–15 ºAPI) in cohesionless sandstones (>30% porosity) can be exploited by permitting sand to enter the wellhole along with fluids. Information from Lloydminster and North Primrose areas is given in Table 1. To achieve sustained production, sand production must be encouraged through use of closely spaced high-energy perforations and through application or work over strategies that re-initiate sand production if it has stopped. Sand exclusion is disastrous; free sand flow is vital production mechanism, as yet incompletely understood(1). Blocking it by gravel packs or screens simply reduces the oil now below economical levels. Lowering Cold Production Costs To compete with offshore oil and absorb price differences between heavy and conventional oil production cost minimization is vital for the shallow (300 – 800 m) heavy oil reservoirs typical of Alberta and Saskatchewan Cretaceous deposit. Drilling costs can be lowered by using coiled tubing and smaller diameter drill hole; there is little evidence that a larger hole is better for cold production. Workover costs can be lowered by using better pumps that do not sand in, and by better workover methods to reduce service TABLE 1: Enhancement of oil rate through cold production. Table Available In Full Paper. rig time and re-establish sand production. Economic and environmentally acceptable sand disposal methods must be implemented(2). Finally, initial development must be planned with EOR production in mind to minimize additional redevelopment costs. Cold Production Mechanisms In these wells, conventional well theory predicts production rates of 0–2 m3/day, rather than the 5– 15 m3/day commonly obtained. Why does heavy oil flow more efficiently if 1–3% sand enters the wellbore with the fluids? A complete answer remains elusive, but the four major factors are likely enhanced drainage radius, grain movement, gas bubble expansion and continuous pore deblocking. Quantitative analyses have been developed for the first two(3, 4), and partly for the third mechanism(5). The fourth remains a qualitative concept. Enhanced drainage arises because thousands of cubic metres of reservoir are affected by large-scale sand production. Discrete cavities may exist, piping tubes may develop, and zones dilated from 30% to 36–40% porosity may all accompany massive sand production. Each of these will increase well flow capacity. Closed-form solutions for piping tube or general yield models show that a factor of 3 to 4 in sustained rate productivity can be expected (3). However, improvement factors of 4 to 10 and more are common in cold production. Grain mobility facilitates liquid movement, independent of permeability enhancement effects. A theoretical model of local fluid rate enhancement in mobile grain systems shows that increased flow rates up to a factor of two can be expected because of the reduction of drag forces(4). There is a variant of the gas bubble theory which may help explain improved production(5).

Enhanced Oil Recovery in North America: Status and Prospects

Abstract This article presents an overview of enhanced oil recovery (EOR) technology in the United States and Canada, ft presents current state-of-the-art of EOR technology, statistics on oil production, number of EOR projects for the past ten years, distribution of EOR production, and EOR projects by various processes. R&D trends and outlook for the near-term future are also discussed.

Experts Assess Status and Outlook for Thermal, Chemical, and CO2 Miscible Flooding Processes

Increased use of enhanced oil-recovery (EOR) technology depends on how competitive EOR oil is with other sources of liquid fuels. Today, with world oil prices at $29/bbl, companies can buy oil reserves in the ground for $5 to $8/bbl. EOR methods cost significantly more-up to about $20/bbl in the case of large chemical floods. Even though the petroleum industry has gained experience and confidence with EOR methods, it is evident that economic conditions are not favorable for any but the least expensive EOR applications. Commercial applications of different EOR processes are evolving at various rates. Steam Flooding is proved commercially; current oil production from these methods exceeds 550,000 B/D (87 400 m3/d), accounting for some 80% of total EOR production. This technology is particularly important in California; recent increases in the state's onshore oil production are attributed mainly to increased steam injection in heavy-oil reservoirs. Michael Prats, Maraven S.A., writes in SPE Monograph Vol. 7, Thermal Recovery: "The potential of thermal recovery processes is much greater than the current production would suggest." One reason is that these processes eventually may unlock the world's huge accumulations of very heavy crudes. Another reason is that thermal methods can be used to displace and recover light crudes; here the limitations are economic - other methods yield a higher rate of return on investment. "There are few known technical reasons for not considering thermal processes for the recovery of any kind of crude," Prats says. They also may be applied to recover shale oil and coal products in situ. Experts Discuss EOR Issues The following comments by members closely involved with EOR processes address the technical status and economic outlook for various methods. Some general observations arise from these specific discussions of Thermal EOR, CO2 flooding, and chemical flooding.

Enhanced Oil-recovery and Its Environmental and Economic Implications in the United States

This survey has described the foreseeable environmental and economic impacts of enhanced oil-recovery (EOR) on U.S. oil production between 1980 and 2000. It has indicated that EOR production may be expected to rise from the approximately 4% of total U.S. oil production in 1980, to the projected approximations of 10.5% in 1985, 18.5% in 1990, 23% in 1995, and perhaps 30% in 2000. These percentages are substantial, particularly as this form of oil production has been, up until recently, quite limited. Many of the processes are still in the laboratory stage of development—particularly chemical and microbiological processes. With continued laboratory experimentation and field research, it is possible that the percentages could be even greater than the above suggestions as we reach into the 21st Century.The potential for EOR is very considerable and probably great, as it could involve some two-thirds of all the oil already identified in the United States and assumed to be unrecoverable by primary or secondary means. The U.S. Department of Energy (DOE) has given important incentives to the EOR industry to make such increased production worth while through raising prices to compensate for the cost of equipment, and deducting expenditure on such equipment from a new ‘Windfall Profit Tax’.Along with EOR's economic potential, there are two major ecological dangers: air pollution through thermal processes, and ground-water pollution through chemical processes. It is essential to the well-being of the United States that clean air standards be adhered to, and that the equipment necessary to purify the air (particularly in California) be available and operate to reduce emissions.A great deal more research needs to be undertaken towards developing safeguards to ensure that drinkingwater is not contaminated by dangerous chemicals which may be used in ‘chemical flooding’ of depleted oil-wells. Many of these chemicals have merely ‘come out of the laboratory’ and are sold by chemical companies without sufficient field-testing. How far these chemicals could travel underground must still be determined. It is also important to ensure that carbon dioxide, fed into a geological formation, can be recaptured and re-injected without escaping into the atmosphere, where there is the potential danger of a global ‘greenhouse effect’ upon the world's temperature. Finally, it is important to safeguard the Earth against microbes which could be injected into its geological strata without sufficient knowledge of their impact on the ecology of the Earth. Thus, much environmental research will be called for with these new methods of producing oil for Man's use.This study has reviewed the four major methods of EOR that are currently being utilized or proposed— thermal processes, miscible and semi-miscible processes, chemical processes, and microbiological processes, and found that they could all have ongoing possibilities.Given appropriate environmental safeguards, EOR should become a major force in the production of energy for the United States over the next 20 years, and it seems reasonable to expect that much the same could apply to other parts of the world. However, it is important that safeguarding the environment should guide the DOE in terms of its incentive programmes for specific processes.