Enhanced Oil Recovery in Eagle Ford: Opportunities Using Huff-n-Puff Technique in Unconventional Reservoirs

Abstract

Although hydraulic fracturing in liquid-rich unconventional reservoirs (LUR) has become a norm, the recovery factor continues to be low. Use of enhanced oil recovery (EOR) techniques in LUR has recently become more popular to improve the recovery. The objective of this study is to numerically investigate the advantages and disadvantages of the application of the CO2 huff-n-puff technique in LUR formations having complex fracture networks. The study explores the fluid flow mechanisms for oil recovery in a naturally fractured reservoir. A calibrated 3D mechanical earth model with geomechanical and petrophysical properties from the Eagle Ford was used for the study. A complex hydraulic fracture model was used to simulate the hydraulic fracture, proppant, and fluid distribution around the wellbore. Numerical reservoir simulation on perpendicular bisection (PEBI) grids was used to capture the permeability, porosity, and conductivity distribution due to the proppants in the hydraulic fractures. The CO2 huff-n-puff technique using numerical reservoir simulation was used to determine the well performance and recovery factor arising from reservoir fluid viscosity reduction and gas expansion. The effect of fluid thermodynamics to recovery systems in the low-permeability reservoir medium was fully captured in this approach. An equation of state prepared for simulating the CO2 impact on the oil was prepared with correlating the collected downhole oil sample. The numerical reservoir simulation study coupled with the complex fracture simulation model presents insights into a new means to improve the recovery factor (RF) in LUR through the injection of CO2. Such EOR method would be critical to increase the long-term economic benefits. The study demonstrates that that infill well requirements can be mitigated if the EOR method of huff-n-puff is utilized in cyclic modes over various time periods of production. Up to 9% extra RF was observed when the CO2 huff-n-puff technique was used as compared to production dependent only on hydraulic fracture stimulation. Parametric sensitivity on job sizes and start timing of EOR in a producing well was used to evaluate the RF. However, the hydraulic fracture geometry and the created footprint along with the time of injection have a larger effect in improving the EOR effectiveness. The methodology demonstrates the simulation of EOR methods in unconventional reservoirs for economic assessment. The workflow demonstrates modeling CO2 flooding as an EOR technique on the full wellbore level with complex hydraulic fracture geometry. The approach can be applied to unconventional formations in other basins to improve the recovery factor.

Implications of Chemical-Thermal enhanced oil recovery methods in shale reservoirs

“…Moreover, they found that due to the misleading of the diffusion mechanism in pilot tests, there are some differences between laboratory and field tests that should be considered in the results. Pankaj et al (2018) investigated fluid flow behaviour mechanisms in fractured reservoirs in the Eagle Ford oilfield. They proposed a 3D petrophysical and geomechanical model to consider the fluid flow through natural fractures and improve the oil recovery by carbon dioxide injection.…”

“…They proposed a 3D petrophysical and geomechanical model to consider the fluid flow through natural fractures and improve the oil recovery by carbon dioxide injection. They concluded that the CO 2 huff-n-puff technique would be an efficient method as the gas phase can mobilize more through the tight pores and spaces (Pankaj et al, 2018).…”

Simulation of High Water-Cut in Tight Oil Reservoirs during Cyclic Gas Injection

“…But no water production data were reported. An important reason is that water-cut for depletion stage is often quite stable except for an initial spike, which is largely due to the flowback to fracturing fluids (Pankaj et al 2018). But sometimes, water cut would surge if induced fractures invaded other zones, such as the overlaying Lodgepole formation in Bakken play (Jin et al 2017) or Bone Spring Formation in Delaware Basin (Pettit and Muirhea 2016).…”

Molecular-Scale Considerations of Enhanced Oil Recovery in Shale

“…Liu et al [35] designed a case study to evaluate the potential of CO 2 -EOR in the Bakken formation where promising results were observed. Pankaj et al [36] devised an Eagle Ford case study to investigate the CO 2 -EOR potential where they refuted the need for infill wells and reported an extra 9% increase in the recovery factor. Kerr et al [37] developed an Eagle Ford case study to engineer single-and multi-well CO2-EOR techniques and reasonable agreement with the field results was reported.…”