Abstract
Cuttings/cores’ Headspace Isotope and Composition Analysis (HICA) provides an effective way to calculate the nano pore throat size and distributions much like nitrogen and CO2 adsorption BET/BJH analysis, and it could also provide information about the original pore pressure or gas in place. Tight gas and oil storage is different from conventional where a majority of oil and gas are stored in nanometer sized pores (nanopores). Therefore the nanofludics, i.e., nanometer scale capillary sealing and opening in nanopores of tight rocks, plays a key role in overpressure conservation and storage of oil and gas, and also the fracing process involves the opening of the nano pore capillary seals through rock-fluid interactions. The rock-fluid nanofluidics interactions during fracing could also be studied through HICA and the results could help the optimization of fracing designs.
Highlights
Unconventional oil and gas production have altered the world oil and gas supply map, in North America where the light oil and gas from tight rocks undergo extensive fracing in the long laterals
With the modeled results above, we developed a protocol that use the dynamic measurements of headspace methane isotope and concentration data to characterize the nano pore throat structure and nano pressures
Very heavy shifts in jars’ headspace methane isotope values in relative to the free mud gas methane isotope values have been observed for core chips as well as cuttings after they were collected in jars during unconventional tight oil and gas drillings
Summary
Unconventional oil and gas production have altered the world oil and gas supply map, in North America where the light oil and gas from tight rocks undergo extensive fracing in the long laterals. We discuss the three puzzles that are not obviously correlated, but are rooted back to the first success of hydraulic fracturing in Barnett shale (Fort Worth Basin, TX) in 1997 [1,2,3], and have been perplexing unconventional tight oil and gas productions, storage and preservation models. These three puzzles are: The shale cuttings and core rocks seems to hold arbitrary amount of gases, for example, even weeks after exhumation and exposed to air, when water droplets are impinged onto the chips and core rocks, there are always gases coming out from the cuttings and core rocks.
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