Nanopetrophysics Characterization of the Mancos Shale Formation in the San Juan Basin of Northwestern New Mexico, U.S.

The Mancos Shale of the San Juan Basin is no stranger to the drilling of oil and gas, but traditional exploration within the region has predominantly been limited to the use of conventional vertical wells. Due to the recent advances in drilling and completion technologies, a large focus of oil and gas exploration has shifted towards the development of unconventional reservoirs. Because of these significant breakthroughs, it comes as no surprise that an increased interest in further developing the Mancos Shale has taken place. However, like most unconventional plays, low porosity and extremely low permeability characterize the Mancos Shale. These characteristics typically result in large production declines of oil and natural gas in the first couple years of production, sometimes up to 90% (Hughes, 2014). One of these issues involves the hindrance in diffusive hydrocarbon transport from the rock matrix to the fracture network (Hu and Ewing, 2014). In order to improve the production of hydrocarbons in these tights reservoirs, it is important to first understand the petrophysical properties of the reservoir itself so that and assessment can be made on the reservoir quality.;This study will provide a better glimpse on the nano-petrophysical properties of pore structure and fluid-rock interactions that implicate hydrocarbon production in tight reservoirs. A suite of tests are performed on core samples from three wells within the Tocito Marine Bar play and the Offshore Mancos Shale play in order to address the relationship between pore structure and the flow and migration of hydrocarbons within the rock matrix. Some of the tests include mercury intrusion capillary porosimetry (MICP), low-pressure gas physisorption, gettability/contact angle, and fluid imbibition. Various attributes of core samples including TOC, XRD, and pyrolysis data are also used to supplement test results to further evaluate reservoir quality.;Results obtained from XRD indicate the Tocito Marine Bar samples are siliceous in nature, compared to the more calcareous Offshore Mancos samples. Tocito Marine Bar samples are found at shallower depths, and were therefore found to be less mature than samples from the deeper, Offshore Mancos Shale play. Contact angle measurements demonstrate that all samples are oil-wet, as n-decane spread readily on to the sample surface. Imbibition tests show good connectivity within the inner pore network with respect to n-decane. Porosity and permeability from various testing methods including MICP, core plugs, and low-pressure gas physisorption show the Mancos Shale is an organic-rich rock with low porosity and low permeability. The Tocito Marine Bar samples display the largest porosity of tested samples ranging from 1.77 to 7.14%, compared to the 1.15% Offshore Mancos sample. Total porosity is influenced primarily by inter-clay platelet pores, organic matter-hosted pores, intragranular pores, and intergranular pores. Porosity and permeability was found to be consistent with results obtained from previous studies, further validating our testing methods.