Enhanced Oil Recovery Method Selection for Shale Oil Based on Numerical Simulations

Abstract

As unconventional reserves, oil shale deposits require additional oil recovery techniques to achieve favorable production levels. The efficiency of a shale reservoir development project is highly dependent on the application of enhanced oil recovery (EOR) techniques. There are many studies devoted to discrete investigations of each EOR method. Most of them claim that one particular method is particularly effective in increasing oil recovery. Despite the wealth of such research, it remains hard to say with certainty which technique would be the most effective when applied in the extraction of unconventional reserves. In this work, we aim to answer this question by means of a comparative study. Three EOR methods were applied and analyzed in the same environment, a single target objectan oil field in Western Siberia characterized by ultra-low permeability (0.03 mD on average) and high organic content. Methods involving huff-and-puff injection of a surfactant solution, hydrocarbon gas, and hot water were studied using numerical reservoir simulations based on preceding laboratory experiments. A single horizontal well having undergone nine-stage hydraulic fracturing was used as the field site model. The comparative calculations of cumulative oil production over an 8-year period revealed that the injection of hot (supercritical) water led to the highest oil recovery in the target shale reservoir. Each EOR method was implemented using the best operation scenario. All three cases resulted in an increase in cumulative oil production compared to the depletion mode, though the efficiency was distinctly different. Twenty-six percent more oil was obtained after hot water injection, 16% after hydrocarbon gas, and 12% after a surfactant solution. Simulation of a hot water huff-and-puff operation over a longer period (43 years) led to a level of oil production 3 times higher than depletion. The drawbacks of each EOR method on the shale site are discussed in the results. A possible solution was proposed for preventing the negative effects of heat loss and water blockage incurred from hot water injection. The comparative study concludes that hot water injection should lead to the highest volume of oil recovery. The conclusions drawn are suggested to be relevant for similar shale fields.

Replica Exchange Molecular Dynamics Simulation of Organic Matter Evolution: From Lignin to Overmature Type III Kerogen

“…While the nature of the minerals, accounting for more than 90% of the mass in shale, is obviously important regarding the efficiency of the hydrofracking process in recovering oil and gas, kerogen is thought to play an essential role. Hydrocarbons are so tightly adsorbed within the kerogen matrix that it is generally assumed that a vast majority (more than 90% in some cases , ) of the hydrocarbons are not recovered due to the low permeability of the kerogen in common shale plays. This has motivated a considerable amount of interest in the properties of kerogen over the past two decades. − …”

Mineral and Fluid Transformation of Hydraulically Fractured Shale: Case Study of Caney Shale in Southern Oklahoma

“…According to the US EIA, 2013 report on recovery from shale oil and shale gas, the ultimate recovery from unconventional reservoirs was less than 25% for natural gas and less than 5% for oil. In a recent publication, Mukhina et al (2021) stated that the ultimate recovery from shale reservoirs is approximately 10% of initial hydrocarbon in place. More research is currently being undertaken aimed at improving the recovery from unconventional hydrocarbon reservoirs.…”

Microscopic Production Characteristics of Pore Crude Oil and Influencing Factors during Enhanced Oil Recovery by Air Injection in Shale Oil Reservoirs

“…As a promising area in global unconventional oil exploration and development, shale oil has received attention as an economic resource due to its great reserve potential. − Shale oil usually refers to the oil resources produced by enrichment in organic-rich shale formations. , By the end of 2021, shale oil production in North America accounted for more than 50%, reaching 4.67 × 10 8 t, and the successful exploration and development of shale oil in North America have contributed to the development of the shale oil theory in China. China contains extremely abundant shale oil resources, which are widely distributed in the Ordos Basin, the Junggar Basin, and the Bohai Bay Basin, and the technically recoverable resources could reach (30–60) × 10 8 t; thus, shale oil has become an important alternative resource in China’s major oilfields for increasing reserves and production. , At present, shale oil is mainly based on the depletion development of horizontal wells and volume fracturing.…”