Pore Structure Petrophysical Characterization of the Upper Cretaceous Oil Shale from the Songliao Basin (NE China) Using Low-Field NMR

Abstract

Low-field NMR theory was employed to study the pore structure of the upper cretaceous oil shale, on the basis of fourteen core samples collected from Qingshankou (UCQ) and Nenjiang (UCN) formations in the Songliao basin. Results indicated that the T 2 spectra from NMR measurements for collected samples contain a dominant peak at T 2 � 1∼10 ms and are able to be categorized as three types-unimodal, bimodal, and trimodal distributions. e various morphologies of T 2 spectra indicate the different pore type and variable connection relationship among pores in shale. By contrast, UCN shale has more single pore type and adsorption pores than UCQ shale. Besides, NMR-based measurements provide reliable characterization on shale porosity, which is verified by the gravimetric approach. Porosities in both UCN and UCQ shales have a wide range (2.3%∼12.5%) and suggest the strong heterogeneity, which partly makes the challenge in selection of the favorable area for shale oil exploration in the Songliao basin. In addition, the pore size of the collected sample has two distribution types, namely, peaked at ∼10 nm and peaked at ∼100 nm. Similarly, two distribution patterns emerge to the specific surface area of the study shale-peaked at ∼2 nm − 1 and peaked at ∼20 nm − 1 . Here, more investigations are needed to clarify this polarization phenomenon. Basically, this study not only exhibits a preliminary understanding on the pore structure of the upper cretaceous oil shale, but also shows the reliability and pertinency of the low-field NMR technique in the petrophysical characterization of the shale oil reservoir. It is expected that this work is helpful to guide the investigation on the pore structure of oil shale from the Songliao basin in theory.

Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

“…Methods. The MicroMR12-025V nuclear magnetic resonance (NMR) laboratory apparatus (Niumag Electronic Technology Co., Ltd.) was operated at a resonance frequency of 11.826 MHz, a magnet temperature of 32 ± 0:02°C, and an echo interval of 0.30 ms [42,43]. Cylinder specimens were measured to be 50 mm in length and 25 mm in diameter.…”

Damage Evolution and Splitting Failure Mechanism of Layered Rock under Dynamic Pulse Load

“…The relationship between the incremental porosity of each pore size and T 2 is called the T 2 spectrum. T 2 spectrum is often used to obtain microscopic information on rock samples. − …”

Evolution of the Anisotropic Thermophysical Performance for Low-Maturity Oil Shales at an Elevated Temperature and Its Implications for Restoring Oil Development

“…31−33 In this basin, the Qingshankou Formation is recognized as one of the promising targeted strata for the shale oil development; another is the Nenjiang Formation. 34,35 The sedimentation of Qingshankou Formation occurred from 92.0 to 86.2 Ma, which was deposited during the post-rift phase characterized by strong subsidence. 33,36 The involved samples were from a shale oil exploration well, where the Qingshankou Formation had a buried depth of ∼1050−1150 m. Thereinto, this work sampled three shale cores with different TOC contents, that is, high (8.72%), middle (4.22%), and low (1.88%), and a relative criterion, which was collected at a depth of ∼1108, ∼1075, and ∼1124 m and contained a vitrinite reflectance (R o ) of 0.92, 0.96, and 0.87%, respectively (Figure 1a), described as low maturity, according to the previous partition criterion about shale oil.…”