As an important stratum of exploration in the Tarim Basin, which is the largest petroleum basin in China, Yingshan Formation has great potential. The relationship between the fine division of microfacies and reservoir space characteristics has not been systematically studied which restricts further exploration. On the basis of the analysis of core, thin section, logging data, imaging logging data (FMI), and field outcrop, the microfacies types and reservoir space characteristics of the Ordovician Yingshan Formation are systemically studied. The results show that (1) nine microfacies (Mf1-Mf9) and four microfacies associations (MA1-MA4) were identified within the Ordovician Yingshan Formation. MA1-MA2 represent a medium- to high-energy sedimentary background, and MA3-MA4 represent a medium- to low-energy sedimentary background. (2) Four reservoir space types were observed in the Yingshan Formation, which are dominated by fracture-dissolution pore type, followed by small dissolution vug type, seldom fracture type, and large-scale karst-cavity type. (3) High-energy microfacies are the material basis of favorable reservoirs. The high-energy microfacies associations are prone to small dissolution vug and fracture-dissolution pore types of reservoirs; large cave reservoirs can sometimes be developed in the high part of the sequence and form favorable reservoirs in the Yingshan Formation. The low-energy microfacies associations mostly appear as original strata or interlayer, but after the superposition of structural cracks, buried karsts, or epigenetic karsts, low-energy microfacies associations may form relatively small-scale fractured and fracture-dissolution pore types of reservoirs in this area.

The western Kunlun Mountains and the adjacent southwestern Tarim Basin define the northwestern boundary of the intensely deformed Cenozoic Tibetan Plateau, and thus should bear important information on the growth processes of the NW Tibetan Plateau. In this study, the integration of a stratigraphic investigation of the Cenozoic Keliyang succession section and a seismostratigraphic analysis on the seismic reflection profile reveal the sedimentary evolution and basin-filling processes of the southwestern Tarim Basin. Our results suggest a significant depositional shift from marine facies during the depositional periods of the Aertashi to Bashibulake Formations to continental facies during the depositional periods of the Keziluoyi to Xiyu Formations. This shift, which corresponds to southward depositional thickening, has been attributed to the uplift of South Kunlun and the onset of foreland basin subsidence along the southwestern Tarim Basin. Strata from the Keziluoyi to Xiyu Formations form an upward-coarsening sequence that is interrupted by a subordinate upward-thinning sequence in the Anjuan Formation. These results, in combination with the northward migration of the depocenter by at least ~56 km since the depositional period of the Artux Formation and previous studies on basinward deformation propagation, demonstrate that the tectonic loading of the western Kunlun has propagated northward to North Kunlun, which suggest expansion of the NW Tibetan Plateau since this period. We posit that the upper-crustal boundary between western Kunlun along the NW Tibetan Plateau and the Tarim Basin is a northward movable feature. This would support the hypothesis that the substantial lower Tarim Plate (>~56 km if calculated from the magnitude of the northward depocenter migration) has underthrusted southward beneath western Kunlun.

The limestone reservoir beds of Late Ordovician Lianglitage Formation are preserved in northwestern Tazhong Uplift of the Tarim Basin with buried depth exceeding 6000 m. The origin of the ultra-deep limestone reservoir is still controversial, which restricts the further hydrocarbon exploration. In order to clarify the main controlling factors of reservoirs, we carried out the study of sedimentary facies, diagenesis, and reservoir characteristics based on seismic, well logging, and core data. The Lianglitage Formation in northwestern Tazhong Uplift is mainly composed of nine lithofacies that are deposited from platform margin reef-shoal, platform-interior shoal, and restricted lagoon to tidal flat environments. The Lianglitage Formation has experienced syndepositional submarine diagenesis, penecontemporaneous diagenesis, and burial diagenesis, and consequently the reservoir space in the formation mainly includes fractures and dissolution vugs and caves. Reef and shoal deposits are the material basis of favorable reservoirs, and the favorable reservoirs have been mostly improved by the dissolution of meteoric water in penecontemporaneous diagenesis. In the burial stage, the early-formed porosity was destroyed by cementation to some extent, but the fractures and associated vugs formed in the late Ordovician and Silurian-Devonian played an important role in the improvement of the reservoir. The results are of great significance to the prediction of deep carbonate reservoirs and the hydrocarbon exploration in basins of western China. Favorable facies, early-stage improvement by meteoric water, and tectonic fracture are key to the formation of high-quality large-scale deep limestone reservoirs.

Fracture is of primary importance to the natural gas production capacity from many tight sandstone reservoirs in the Kuqa foreland basin, NW China, but the orientation, size and plane porosity of the fractures in the subsurface is difficult to measure directly. Terrestrial light detection and ranging (LIDAR) surveys can offer factual information of outcrop-based research efforts to characterize fracture development laws and controlling factors. In this paper, utilizing a multi-level covering, we obtain the three dimensional (3D) point cloud data from a LIDAR survey launched at a typical outcrop. Matching with high-resolution digital photos and artificial measured information, the 3-D positions of natural fractures are extracted strictly in the data volume section. Furthermore, the fracture and reservoir model can be founded based on the systematic sampling and laboratory analysis, while a variety of accurate facture parameters can be obtained. It is founded that three groups of shear fractures are mainly developed in two periods with large inclination, short trace length and small spacing of normal distribution. Its patterns has provided a literal distribution of penetrating fracture zone and interlayer fracture zone with a single and a double set of advantage orientation respectively. It turned out that the fracture development scale is controlled by lithology, layer thickness, maximum principle paleostress and rock composition with a good exponential relationship. Our work could provide a workflow linking outcrop fracture observations to the 3D model of subsurface fracture prediction and extend modeling capability in other outcrop studies.