Fine Description Of Microscopic Features On Nanopore Throat For Tight Sandstone In Northern Of Honggang, Fuyu Oil Layer Of Songliao Basin

Abstract

Research on the K1q4 member of the petroliferous Fuyu Formation of northern of Honggang in Songlian Basin, has focused on the type, size and form of micro pore structure in the tight sandstone reservoir, also, the mineral surface porosity of the and pore size distribution of nanopores. The results show that the average porosity is 7.27%, permeability average is 0.25×10-3 micrometer2, thus it belongs to low porosity, ultra low and low permeability tight reservoir. The pore structure of this reservoir is complex, as a whole with poor connectivity. Rore-throat radius is small, mainly distributed between 0.025 ∼ 0.63 microns and sorting is bad. There are three types of nanopores developed in this area: grain micropore, mineral intragranular pore and microfracture. The grain micropore include the hairline nanopore of goeschwitzite mica (grain size: 204-714 nm), slit shape nanopore of chlorite (grain size: 81-800 nm) and quartz nanopore (grain size: 200-800 nm). Mineral intragranular pore include pitted quartz (grain size: 42-407 nm) and pits in feldspar (grain size: 352 nm-1.55 microns). Microfracture contain the fissure in granules (width: 31-154 nm) and around the edge (width: 135-540 nm). Meanwhile, twelve forms of nanopores were discovered: slit, mesh, short slit, beaded, triangular, nearly spherical pits, trapezoidal, pin-hole, pore shape, strip shape, linear, serrated, and wedge-oblong. However, the pores distribute independently with poor connectivity. We define mineral surface rate as the ratio of visible pore area over the surface area in a image. This parameter of main minerals have been measured in this area and find that the ratio for quartz is 0.36% and feldspar is 1.9%. Therefore, feldspar has better storage space in its mineral surface. Three samples of tight sandstone were measured by nitrogen adsorption and show that the more abundant larger nanopores, the better the porosity and permeability of the samples. Baed on this study of the nanoporosity of the Fuyu reservoir, we conclude that exploration and development of unconventional oil and gas in Songliao basin has great potential.

AAPG Datapages/Search and Discovery Article #90215 © 2015 Pacific Section AAPG Convention, Oxnard, California, May 3-6, 2015