Search

The reservoir architecture analysis of braided rivers, especially falling-silt seam forms, has played a key role in predicting remaining oil distributions. However, no studies have used architecture analyses that document braided river outcrops and researched the tapping of the few remaining oil distributions based on outcrops in the Songliao basin, northeast China. In this paper, the architecture characteristics and remaining oil distribution of braided river reservoirs are studied using a combination of an outcrop, modern deposition and subsurface well data. The new 8–13 m thick Lower Cretaceous Quantou Formation outcrop of the Songliao basin is a braided fluvial succession arranged in one large fining-upward cycle. Eight facies (Gt, St, Sm, Sh, Sp, Sw, Fl and Fm), four architecture elements (CH, DA, LV, and FF), and three orders of bounding surfaces (third-, fourth-, and fifth-order) are recognized. A new distribution pattern of falling-silt seams and a braided river architecture model are presented according to the analysis of the outcrop. In the mid-channel bar, the falling-silt seams thin from the mid-bar to the bar tail following the flow direction. Each falling-silt seam is oriented tangentially to the basal surface of the mid-channel bar, and the upper falling-silt seam extends farther than the lower one. In a Daqing Oilfield exploitation block in the Songliao basin, while channels and bars are the main reservoir units, they have different remaining oil distribution patterns. For bars, water injection wells located at the mid-bar, zonal injection technology, the drilling of horizontal wells, and proper well patterns are proposed. Fourth-order bounding surfaces, single braided channels, stacking patterns, and the lateral blocking of levees and floodplains are the key factors affecting the remaining oil distribution in channels.

Just as in deep-water sedimentary environments, productive source rocks can be developed in an evaporitic platform, where claystones are interbedded with evaporites and carbonates. However, the impact of the paleoenvironment on the organic matter enrichment of shallow water source rocks in an evaporite series has not been well explored. In this study, two wells in the central uplift of the Tarim Basin were systematically sampled and analyzed for a basic geochemical study, including major elements, trace elements, and total organic carbon (TOC), to understand the relationship between TOC and the paleoenvironmental parameters, such as paleosalinity, redox, paleoclimate, paleo-seawater depth, and paleoproductivity. The results show that the Lower–Middle Cambrian mainly developed in a fluctuating salinity, weak anoxic to anoxic, continuous dry and hot, and proper shallow water environment. The interfingering section of evaporites, carbonates, and claystones of the Awatag Fm. have higher paleoproductivity and higher enrichment of organic matter. Paleosalinity, redox, paleoclimate, paleo-seawater depth, and paleoproductivity jointly control the organic matter enrichment of shallow water source rocks in the evaporite series. The degree of enrichment of organic matter in shallow water source rocks first increases and then decreases with the increase in paleosalinity. All the samples with high content of organic matter come from the shallower environment of the Awatag Fm.

Background and Aims: To evaluate the diagnostic performance of dual elastography (dual-elasto) in continuous differentiation of liver fibrosis and inflammation in a large prospective cohort of patients with chronic HBV., Approach and Results: Adults with positive HBsAg for at least 6 months were recruited from 12 medical centers. Participants underwent dual-elasto evaluations. Biopsy was performed 3 days after dual-elasto examination. Four logistic regression models were trained and strung together into series models. Decision trees based on the series models were performed to achieve continuous differentiation of liver fibrosis and inflammation. The influence of inflammation on the fibrosis stage was also evaluated. A total of 560 patients were included in the training set and 240 in the validation set. Areas under the receiver operating characteristic curve of the series model were 0.82, 0.86, 0.93, and 0.96 to predict ≥F1, ≥F2, ≥F3, and F4 in the validation set, which were significantly higher than those of serum markers and shear wave elastography (all p < 0.05), except for the ≥ F1 levels ( p = 0.09). The AUCs of the series model were 0.93, 0.86, 0.95, and 0.84 to predict inflammation stages ≥G1, ≥G2, ≥G3, and G4, respectively. Decision trees realized 5 continuous classifications of fibrosis and inflammation. Inflammation could enhance the mild fibrosis stage classification while showing limited influences on severe fibrosis or cirrhosis diagnosis., Conclusions: Dual-elasto demonstrated high performance in the continuous discrimination of fibrosis and inflammation in patients with HBV and could be used to diagnose mild fibrosis without the influence of inflammation., (Copyright © 2023 American Association for the Study of Liver Diseases.)