Primary oil recovery from fractured unconventional formations, such as shale or tight sands, is typically less than 10%. The development of an economically viable enhanced oil recovery (EOR) techni...

A Literature Review of CO2, Natural Gas, and Water-Based Fluids for Enhanced Oil Recovery in Unconventional Reservoirs

A review of microscopic seepage mechanism for shale gas extracted by supercritical CO2 flooding

Ecological risk assessment of soil and water loss by thermal enhanced methane recovery: Numerical study using two-phase flow simulation

Review of CO2 injection techniques for enhanced shale gas recovery: Prospect and challenges

To investigate the impact of fluid viscosity and rock heterogeneity on the characteristics (such as geometric complexity, roughness, and micro-morphology) of hydraulic fractures (HFs), laboratory triaxial fracturing experiments were conducted on homogeneous and layered tight sandstones using water- and carbon dioxide (CO2)-based fluids. The fractal dimension of HFs (Df) and the stimulated fracture area were quantitatively analyzed based on computerized tomography scanning and three-dimensional reconstruction methods. The surface roughness and micro-characteristics of HFs were then evaluated. Experimental results showed that CO2-based fracturing tended to create more HFs with a higher degree of geometric complexity (Df ranging 2.1113–2.2271) than that of HFs created by water-based fracturing (Df ranging 2.0952–2.1081) in a homogeneous tight sandstone. A complex HF network (Df = 2.4092) was generated in the layered tight sandstone using supercritical CO2 (SC-CO2) fracturing. The SC-CO2-induced fracture area in the layered tight sandstone was approximately three times larger than that of the homogeneous tight sandstone. Both the fluid viscosity and particle size of the host rock have a great effect on the roughness of the HF surface. CO2-based fracturing tends to generate curved HFs with uneven and cracked HF surfaces and massive microfractures, whereas water-based fracturing is more likely to induce straightforward HFs with smooth and clean HF surfaces and few microfractures. These induced microfractures enhance the micro-complexity of HFs, which may contribute to additional conductivity in the production stage. The obtained results provide a laboratory research basis for fracturing fluid selection and fracturing treatment design in tight sandstone reservoirs.

Hydraulic Fractures Induced by Water-/Carbon Dioxide-Based Fluids in Tight Sandstones

Investigating the role of water on CO2-Utica Shale interactions for carbon storage and shale gas extraction activities – Evidence for pore scale alterations

Quantifying dry supercritical CO2-induced changes of the Utica Shale

An Assessment of the Dynamic Moduli of Atmospherically Generated Foam Cements


 The objective of this paper is to evaluate the physical and dynamic mechanical properties of foamed cement generated at a field site and compare them to similar cements fabricated within the laboratory. Physical and mechanical properties such as porosity, permeability, Young's modulus, Poisson's ratio, bulk modulus, shear modulus, etc. will be discussed. Mechanical properties were obtained under cyclic confining pressures ranging from 12 – 52 MPa. This paper will document the final results of a long-term project that examined the differences between foamed cements generated with laboratory equipment and field foamed cementing equipment. The cement samples in this study were generated at pressure using field foamed cementing equipment as part of a joint effort between the API Sub-Committee 10 and the National Energy Technology Laboratory (NETL). The samples were characterized using helium porosimetry, ultrasonic velocity, and permeability measurements after they were depressurized. To test the variation in permeability and strength parameters of various foam cements, stepwise loading and unloading experiments were conducted. Effective pressures varied between ≈6.8 MPa to ≈46 MPa in ≈4 MPa increments. Permeability was measured at each effective pressure step to determine the change in flow pathways due to cyclic confining pressures. Dynamic moduli including Poisson's ratio and Young's modulus were calculated to determine the impact of effective pressures on the flexibility of the cement. The data shows that the cement's physical and mechanical behavior varied along the length of the sampling containers. During the initial loading of some of the samples, permeability decreased to a point lower than the initial permeability and stayed constant for the remainder of the pressure cycle, which was observed in previous experiments. However, some of the permeability values increased suggesting that the pressure cycles had permanently reconfigured the internal structure of the samples. Our approach to evaluating foamed cement is somewhat novel in that we have collaborated with the API, operators, and service companies, to obtain foamed cement generated at pressure using field equipment enabling a robust comparison to those generated in a laboratory per the API's RP 10-4B. Not only will the information provided by these comparisons help to facilitate the better design and implementation of foam cement generation processes but it will also help improve the understanding of the physical and mechanical behavior of foam cement.

Jim Fazio

Papers

Investigating the role of water on CO2-Utica Shale interactions for carbon storage and shale gas extraction activities – Evidence for pore scale alterations

Quantifying dry supercritical CO2-induced changes of the Utica Shale

An Assessment of the Dynamic Moduli of Atmospherically Generated Foam Cements

An Assessment of the Physical and Mechanical Properties of Foamed Cement Generated at a Field Site vs. Laboratory