An Experimental Investigation of WAG Injection in a Carbonate Reservoir and Prediction of the Recovery Factor Using Genetic Programming

Abstract

Production from mature oil fields is gradually declining, and new discoveries are not sufficient to meet the growing demand for oil products. Hence, enhanced oil recovery is emerging as an essential link in the global oil industry. This paper aims to recognize the possibility of increasing oil recovery from Polish carbonate reservoirs by the water alternating gas injection process (WAG) using various types of gases, including CO2, acid gas (a mixture of CO2 and H2S of 70/30% vol/vol) and high-nitrogen natural gases occurring in the Polish Lowlands. A series of 17 core flooding experiments were performed under the temperature of 126 °C, and at pressures of 270 and 170 bar on composite carbonate cores consisting of four dolomite core plugs. Original reservoir rock and fluids were used. A set of slim tube tests was conducted to determine the miscibility conditions of the injected fluids with reservoir oil. The WAG process was compared to continuous gas injection (CGI) and continuous water injection (CWI) and was proven to be more effective. CO2 WAG injection resulted in a recovery factor (RF) of up to 82%, where the high nitrogen natural gas WAG injection was less effective with the highest recovery of 70%. Based on the core flooding results and through implementing a genetic programming algorithm, a mathematical model was developed to estimate recovery factors using variables specific to a given WAG scheme.

Overview of Methods for Enhanced Oil Recovery from Conventional and Unconventional Reservoirs

“…As mentioned above, the use of injection of heat carriers into the reservoir is associated with high-energy costs and therefore increases the cost of production. Professor V. I. Kudinov and his collaborators have developed and implemented in Udmurtneftegaz software (v2.0) improved methods of thermal action along with changing time cycles and using chemical reagents to increase oil recovery in complex reservoirs [13,76].…”

Improving the Efficiency of Oil Recovery in Research and Development

“…During the improvement of oil recovery, one of the basic problems accompanying the use of water in EOR processes is the precipitation of inorganic sediments [15]. As the authors write in the publication [16], these are the most common deposits of calcium carbonate and deposits of calcium, barium and strontium sulphates, with calcium carbonate being the most common one [17,18]. In order to eliminate this unfavorable phenomenon, appropriate types of inhibitors are used, which was presented in the publication [16].…”

“…As the authors write in the publication [16], these are the most common deposits of calcium carbonate and deposits of calcium, barium and strontium sulphates, with calcium carbonate being the most common one [17,18]. In order to eliminate this unfavorable phenomenon, appropriate types of inhibitors are used, which was presented in the publication [16]. However, in order to carry out such tests, it is necessary to develop the research technology and build a test stand.…”

“…However, in order to carry out such tests, it is necessary to develop the research technology and build a test stand. Such a solution was presented by the authors of the publication [16] and they discussed the most important research results.…”

The effect of NaCl and HPAM solution concentration on HPAM gel structure degradation by ultrasonic waves

“…With discoveries of new oil fields decreasing and the demand for oil rising, utilizing mature oil reservoirs has become increasingly important. [1,2] Techniques such as improved oil recovery (IOR) and enhanced oil recovery (EOR) are used to extract residual oil from these older fields. [3][4][5] While these methods are commonly used, they can still present challenges, such as a high water production, which increases operational costs.…”