Eagle Ford Huff ‘n’ Puff Gas-Injection Pilot: Comparison of Reservoir-Simulation, Material Balance, and Real Performance of the Pilot Well

Abstract

Summary In this study we compare real data from an Eagle Ford Shale huff ‘n’ puff (H&P) gas-injection pilot with reservoir simulation and tank material-balance calculations. The comparison is good and supports the conclusion that oil recovery from the Eagle Ford (and likely other shales) can be increased significantly using H&P. For H&P to work, the injected gas and the in-situ oil in the shale must be contained vertically and laterally following hydraulic fracturing. Containment is critical for the success of H&P. Containment implies that the injected gas flows into the hydraulic fractures, penetrates the tight matrix, and does not escape or leak outside the target stimulated reservoir volume (SRV). Vertical and lateral containment exists in the Eagle Ford as demonstrated previously (Ramirez and Aguilera 2016) with an upside-down distribution of fluids: Natural gas is at the bottom of the structure, condensate in the middle, and oil at the top. Two different matching and forecasting approaches are used in this study: reservoir simulation and tank-material-balance calculations. The results show a good history match of primary recovery and secondary recovery by H&P in the pilot well. The history match is good in the case of both reservoir simulation and tank material-balance calculations. Once a match is obtained, the simulation and material balance are used to forecast secondary recovery over a period of 10 years with sustained H&P injection of dry gas. The results indicate that dry-gas H&P can increase oil recovery from the Eagle Ford Shale significantly. Under favorable conditions, oil recovery can be doubled and even tripled over time compared with the primary recovery. The addition of heavier ends to the H&P gas injection can increase oil recovery even more, putting it on par with recoveries in conventional reservoirs. The benefit of H&P occurs in the case of both immiscible and miscible gas injection. The H&P benefits can likely be also obtained in other shale reservoirs with upside-down containment of dry gas, condensate, and oil. The novelty of this work is the combined use of reservoir simulation and tank material-balance calculations to match the performance of an H&P gas-injection pilot in the Eagle Ford Shale of Texas. We conclude that oil recoveries can be increased significantly by H&P.

Origin, transport, accumulation of methane in sedimentary basins revisited

“…This differs from the production of gas from conventional gas reservoirs where the gas/water ratio declines during production. (Jarvie, 2012;2015) and other attempts to predict the shale gas production profile from first principles have not been successful (Kuske et al, 2019;Orozco et al, 2020). However, if we accept that most of the gas is produced from the mudstone, the shale gas production profile can be understood as reflecting the increased connectivity of initially isolated gas pockets due to reduced pressure from production.…”

“…The in-situ separation of oil and gas can also explain why in "Huff'n Puff" gas injection (Orozco et al, 2020) results in a doubling of oil recovery (from 10 to 20%), while most of the injected gas remains in the ground. Attempts to model the experience from first principles have not been successful (Orozco et al, 2020).…”

“…The in-situ separation of oil and gas can also explain why in "Huff'n Puff" gas injection (Orozco et al, 2020) results in a doubling of oil recovery (from 10 to 20%), while most of the injected gas remains in the ground. Attempts to model the experience from first principles have not been successful (Orozco et al, 2020). If we assume that the oil is confined to the organic laminae and that most of the injected gas invades the organic laminae (because there is no capillary entry pressure), invasion of gas will substitute for and mobilize some of the oil adsorbed on the organic matter.…”

Conformance Control for Tight Oil Cyclic Gas Injection Using Foam

“…Cyclic gas injection or gas huff and puff has been proposed to enhance the oil recovery in tight oil reservoirs [1][2][3][4]. It is implemented through injecting certain type of gas into the multistage hydraulically fractured horizontal well, soaked for some time, and produced back from the same well.…”

A Laboratory Approach to Measure Enhanced Gas Recovery from a Tight Gas Reservoir during Supercritical Carbon Dioxide Injection

“…Unconventional reservoirs include shale reservoirs, tight (k < 10 mD) or ultra-tight (0.1 < k < 1 mD) reservoirs [46][47][48][49][50]. Due to tight gas reservoirs' low permeability and poor reservoir characteristics [51][52][53][54][55], ultimate gas recovery is very low, which is not beneficial for petroleum industries [56][57][58][59][60][61]. Various studies have been conducted on the gas recovery enhancement from tight gas reservoirs; however, there is no significant progress made, compared with conventional gas reservoirs [62][63][64][65][66][67].…”