From Correlation to Causality

The impact unconventional plays have had in the energy industry has been nothing short of revolutionary. The presence of source rocks has long been known. Shale extraction technologies have matured, such as horizontal drilling and multi-stage hydraulic fracturing, and their correlation to oil and gas recovery is well understood. However, even after billions of dollars invested and billions of barrels of oil produced from these nano pore reservoirs, the causality between many of the variables responsible for production still remains unknown or uncertain:

  1. How is oil released from nano sized matrix pores?

  2. Is gas release good for oil recovery?

  3. Does fluid composition matter?

  4. What is the technical limit for oil and gas recovery?

This paper describes the application of digital rock technology in the Eagle Ford unconventional shale play in Texas. Consistent with the findings of thousands of papers written on the Eagle Ford, the reservoir is generally described as a world-class source rock. A typical well has a horizontal lateral exceeding 5500 ft and is fractured with a multiple of different pump designs. Oil and gas is produced through fracture networks reactivated by hydraulic fracturing, connected to the tight matrix that serves as storage. The release and transport of oil and gas from the nano porosity matrix to the fractures are processes that are not well understood. These processes are complex and include specific nano scale phenomena and mechanisms.

Direct Hydrodynamic Simulation (DHD) – Modeling with Density Functional Hydrodynamics

Understanding complex fluids and hydrodynamic processes in nano pore systems remain a key challenge to effective development of shale plays. Physical sampling and laboratory measurements are crucial to understand the reservoir rock and fluids, but are costly and time consuming and, more often than not, provide only partial answers. Digital rock technology can complement the physical testing and provide important insights into understanding the source rock reservoir. Recent publications show a growing interest in nano-scale hydrodynamics and describe processes to better understand the multiphase transport in rocks with pore throats of 5 to 100 nanometers in size. Studies have shown that when working in nano-scale hydrodynamics there are additional phenomena that must be considered. The range of physical phenomena is studied and understood separately (Bhushan, 2004), but an integrated approach that can incorporate them in a unified way is lacking.

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