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Honghe oilfield is located in the southern Tianhuan Depression of the Ordos Basin. The Upper Triassic Yanchang Formation is in a normal or negative pressure state. The reservoir is tight with low permeability. The time relationship between reservoir densification and formation is very important in the dynamic mechanism analysis of hydrocarbon accumulation in tight sandstones. Combined with microfacies analysis of fluid inclusions, isotopic chronology of authigenic illite, numerical simulation of hydrocarbon generation evolution, and observation statistics under a microscope, this relationship is studied in the Yanchang Formation, and the reservoir forming mechanism of a tight sandstone under low dynamic background is analyzed. The results show that diagenesis and oil accumulation of the Yanchang Formation in the Honghe oilfield occur synergistically, and large-scale reservoir formation is earlier than the key densification event. The Yanchang Formation reservoir is the result of early filling, dominant channel, differential pressure driving, and other mechanisms under a low dynamic background, which shows the characteristics of early selective filling, late inherited filling, and disseminated expansion. The coupling evolution relationship between reservoir forming dynamics and resistance of different sandstones determines the differential accumulation and enrichment of strongly heterogeneous reservoirs. [ABSTRACT FROM AUTHOR]

The Chang 8 member of the Upper Triassic Yanchang Formation is the main oil layer in the Zhenjing area in the southern Ordos Basin. The reservoir rock of the Chang 8 member is mainly typical distributary channel sandstone in a delta front, of lithological reservoir type. The reservoir is dense and low-permeability, with strong heterogeneity, and it shows major changes in oil saturation. The study of reservoir heterogeneity is of great significance for understanding the internal structure and formation mechanism and for the prediction of sweet points in the reservoir. The degree of heterogeneity and genetic mechanism of the reservoir were analyzed, and a model of the structural heterogeneity of a tight sandstone reservoir was established. The results indicate very marked heterogeneity in the Chang 8 member reservoir, showing erosion and disorderly overlapping of the channel sandbodies over multiple periods. Even within the same thick, massive sandbody, there are considerable differences in physical and oil-bearing properties. The heterogeneity of a clastic reservoir is a result of the spatial distribution of fine-grained sedimentary interlayering, soft lithic sandstone and calcareous tightly cemented sandstone. These properties are due to the changes in different sand channels at different times, the differential diagenetic evolution of different types sandstones and selective filling of oil. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effectiveness of butterfly shaped locking compression plate for the treatment of complex distal radius fractures., Methods: Between June 2011 and January 2013, 20 cases of complex distal radius fractures were treated with butterfly shaped locking compression plate fixation. There were 11 males and 9 females with an average age of 54 years (range, 25-75 years). Injury was caused by falling in 10 cases, by traffic accident in 7 cases, and by falling from height in 3 cases. All of fractures were closed. According to AO classification system, there were 8 cases of type C1, 8 cases of type C2, and 4 cases of type C3. Of them, 9 cases had radial styloid process fracture, 4 cases had sigmoid notch fracture, and 7 cases had both radial styloid process fracture and sigmoid notch fracture. The mean interval between injury and operation was 5.2 days (range, 3-15 days)., Results: All incisions healed by first intention; no complications of infection and necrosis occurred. All cases were followed up 14 months on average (range, 10-22 months). All factures healed after 9.3 weeks on average (range, 6-11 weeks). No complications such as displacement of fracture, joint surface subsidence, shortening of the radius, and carpal tunnel syndrome were found during follow-up. At last follow-up, the mean palmar tilt angle was 10.2° (range, 7-15°), and the mean ulnar deviation angle was 21.8° (range, 17-24°). The mean range of motion of the wrist was 45.3° (range, 35-68°) in dorsal extension, 53.5° (range, 40-78°) in palmar flexion, 19.8° (range, 12-27°) in radial inclination, 26.6° (range, 18-31°) in ulnar inclination, 70.2° (range, 45-90°) in pronation, and 68.4° (range, 25-88°) in supination. According to the Dienst scoring system, the results were excellent in 8 cases, good in 10 cases, and fair in 2 cases, and the excellent and good rate was 90%., Conclusion: Treatment of complex distal radius fractures with butterfly shaped locking compression plate can reconstruct normal anatomic structures, especially for radial styloid process and sigmoid notch fractures, and it can get good functional recovery of the wrist and the distal radioulnar joint.

Objective: To discuss the clinical result of extrinsic radioulnar tether combined with anchoring nail fixation for treating chronic dorsal instability of the distal radioulnar joint (DRUJ)., Methods: Between July 2011 and December 2012, 6 patients with chronic dorsal instability of the DRUJ were treated with extrinsic radioulnar tether combined with anchoring nail fixation. There were 1 male and 5 females with the average age of 27.3 years (range, 22-35 years). All of 6 patients had a wrist trauma history. The average disease duration was 4.8 years (range, 6 months to 15 years). Radiographs were taken postoperatively to observe the anchoring nail loosening. The stress test and forearm rotation test were used to evaluate the function of DRUJ. The complications, the grip power, range of motion, and visual analogue scale (VAS) scores were recorded at last follow-up. And the joint function was evaluated by disability of arm, shoulder, and hand (DASH) score., Results: Primary healing of incision was obtained in all cases, without any complications such as infection and ulnar neck fracture. All 6 patients were followed up 6-24 months (mean, 13.7 months). Stability was achieved in all patients. Radiographs showed that the joint space was widened and dislocation of the ulnar head was improved at 3 and 6 months after operation. The results of the stress test and forearm rotation test were negative. At last follow-up, the grip power, DASH score, VAS score, and range of motion of the wrist were significantly improved when compared with preoperative ones (P < 0.05)., Conclusion: Extrinsic radioulnar tether combined with anchoring nail fixation is an easy method of surgical revision to treat chronic dorsal instability of DRUJ, which can maintain the stability and protect the blood supply of triangular fibrocartilage complex.