查看更多>>摘要：In directional drilling, torque fluctuation generates a big shock when using polycrystalline diamond compact (PDC) bits, causing problems such as instability in vibration tools. This study presents a new type of composite bit with a roller on the blade. The mechanism of torsion reduction and vibration of the roller PDC hybrid bit is studied through a rock breaking experiment on the roller unit and a comprehensive drilling experiment on the composite bit. Six roller contour shapes, different pressures into the depth of the roller, six roller radial positions and the relative height of roller teeth, and PDC cutters that affect the novel hybrid torsion on bit (TOB) and weight on bit (WOB) are investigated. The equivalent friction coefficient of the roller and axial force per unit depth is used to evaluate the torsional and vibration reduction ability of the Roller. The results show that the equivalent friction coefficient of different contour Rollers is lower than that of PDC cutters, and the torsion reduction ability of the Rollers is higher than that of PDC cutters. The vibration reduction in the roller teeth in different radial positions was 1.59-9.17 times higher than that of PDC cutters, The torque of the roller PDC hybrid bit is 71.72%-98.33% of the conventional PDC bit. The roller shares 1.59%~(-2)3.06% of the WOB of the whole bit. As the cutter teeth and the PDC cutter's relative height decreases, the compound drilling torque decreases, the roller bit's weight proportion gradually increases, the torsional capacity decreases, and the damping capacity increases.
查看更多>>摘要：The sequence architecture and depositional evolution in Cenozoic Liaodong Bay, Bohai Bay Basin are formed mainly in response to rifting and lacustrine fluctuations which have been documented by integrated analysis of seismic reflections, well logs, lithology associations and core analysis. Four depositional-geomorphological systems are identified comprising fan delta systems, near-shore subaqueous fan systems, beach-bar systems and braided river delta systems. Three composite sequences (CS) are recognized including CS IV (S4), CS III (S3-3, S3~(-2), S3-1), and CS II (S2). The identification and description of sequence boundaries in different composite sequences vary from each other due to database. CS IV (S4) is difficult to identify across the whole area. CS III (S3-3, S3~(-2), S3~(-1)) is bounded by regional unconformities along the slope or on the uplift and correlative conformities in the central depression. CS II (S2) is locally bounded by regional unconformities according to seismic resolution. The geomorphical processes and fault activities, during different stages of rifting, in addition to overlapping effects of lacustrine fluctuations, sediment supply and climate changes control composite sequences and depositional-geomorphological systems. Finally, fan delta systems and braided river delta systems are proposed to host petroleum reserves.
查看更多>>摘要：Oil seep samples from Abu-Jir Fault Zone (AJEZ) were geochemically characterized to determine the level of biodegradation and the depositional environment of correlative source rocks. For this purpose, saturated and aromatic biomarkers and stable carbon isotopes of thirteen samples were analyzed and measured. Saturated hydrocarbons of the AJFZ are low;; whereas polar fractions are relatively high. Normal alkanes and isoprenoids of these oil seeps are totally removed;; steranes are still intact in some samples, and slightly to heavily degraded in other samples;; whereas hopanes are intact These criteria indicate that these samples are moderately to heavily biodegraded. low C24./C23, high C22/C21 tricyclic terpanes and C29/C_(30) hopane ratios suggest that these oil seeps were generated from carbonate source rocks. In addition, the high C35/C34 hopanes and homohopane index values suggest deposition under marine anoxic conditions. Low values of diasteranes/regular steranes, Ts/Tm, and moretane/hopane for most samples suggest early-mature source rocks. Sterane distributions and carbon isotopic composition of the AJEZ oil seep samples suggest they are not genetically related with the oils of the southern oilfields (Majnoon, Nasiriyah, West Qurna, North Rumaila, Luhais, Abu Gharab, Faka, Buzergan), nor consistent with the main source rocks (Sargelu and Naokelekan), but they are closely related to the East Baghdad oilfield and Chia Gara extracts. This study suggests the oil seeps were generated from Chia Gara Formation (upper Jurassic-lower Cretaceous).
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