Water consumption in hydrocarbon generation and its significance to reservoir formation

The geochemical effects of water consumption during hydrocarbon generation were studied on the basis of evolution laws of source rocks and simulation experiments on hydrocarbon generation. Water consumption statistics were obtained in order to study the relationship between water consumption during hydrocarbon generation and hydrocarbon migration and reservoir formation. The simulation experiments of hydrocarbon generation were performed under hydrous and anhydrous conditions for correlation. The geochemical characteristics of organic evolution under these two conditions were analyzed and the variations of hydrocarbon generation potential and carbon transformation ratio were emphasized. The results show the effects that organic matter and water have on each other during hydrocarbon generation: part of unavailable carbon is activated in kerogen and hydrogen is increased in degraded products, which leads to the increase of total hydrocarbon generation potential. According to water consumption mechanisms, the quantitative evaluation method of water consumption in hydrocarbon generation was put forward and used in the studies of the main source rocks in the Dongying Sag. Both of the water consumption and the depth range of the Upper Es4 Member are larger, while those of the Lower and Middle Es3 Members are smaller. Water consumption affects hydrocarbon migration and accumulation by increasing organic carbon degradation rate to increase fluid volume. Pore fluid pressure and oil-bearing saturation are consequently increased. The matching relationship between water-consuming hydrocarbon generation intervals and water-consuming diagenesis intervals enhances the dynamic forces of hydrocarbon migration, which benefits the formation of self-generating and self-preserving reservoirs or lower-generating and upper-preserving reservoirs. Key words: hydrocarbon generation, water consumption, reservoir formation, simulation, Dongying Sa

Control of pressure system development on reservoir formation in the Dongying Sag, Shengli Oilfield, East China

The zonality of abnormal pressure is closely correspondent to the breakthrough pressure (or pressure preservative ability) of mudstones in the Dongying Sag. The breakthrough pressures and formation fluid pressure coefficients rise with increasing depth. The preservation of isolated mudstone intervals is also important to the abnormal pressure formation. Based on the episodic difference of pressure buildup mechanism, source dynamic (fluid pressure in source rocks) fields of critical geologic times were analyzed in lateral plane and vertical profiles in the Dongying Sag. Source dynamic of major source rocks occurs in disequilibrium with time and space, which affects oil-gas sources and reservoir formation and controls the direction of oil-gas migration as a whole. The present reservoirs are distributed along the pressure decreasing directions. The distribution of the reservoirs is successional to the evolution of source dynamic. On the other hand, oil-gas migration and accumulation affect the distribution of formation pressure fields. The isolated mudstone intervals preserve the fluid pressures to different extents. Due to the equilibrium between pressure buildup and pressure relief, source dynamic creates different conditions in various pressure systems during its transference, which cause the differences in types and features of oil-gas reservoirs. Based on the evolutionary history of source dynamic, the reservoir forming process in the Dongying Sag was analyzed. The deep layers of the Shahejie Formation are important targets for us to discover light hydrocarbon and natural gas reservoirs with high pressures. 摘 要: 东营凹陷异常压力的分带性与泥岩的突破压力（或保存能力）具有明显的对应关系，随着深度增加，泥岩突破压力及地层流体压力系数均增大，泥岩封隔层对流体压力的保存也是形成异常压力的重要条件。基于增压机制的阶段性差异，对东营凹陷平面上及典型剖面中重要地质历史时期源动力（烃源岩流体压力）场进行了分析，主力烃源岩的源动力在时间和空间上发育不均衡，从整体上影响了储集层油气来源及油藏的形成，控制了油气运移的方向。现今油藏总体沿地质历史时期源动力场降低的方向分布，表现出油藏的分布与源动力的演化具有一定的继承性；油气运移和成藏也影响了地层压力场的分布，高压油气运移到储集层后，其泥岩封隔层不同程度地保存了流体压力。由于增压-卸压的平衡关系，源动力传递过程中在不同压力系统中构成了不同的动力条件，造成了各压力系统中油气成藏类型和特征具有一定的差异性。根据源动力的演化史，指出沙河街组深层是寻找高压轻质油藏及天然气藏的重要目标。 Key words: Dongying Sag, palaeopressure, petroleum accumulation, controlling, fillin

Movability of lacustrine shale oil: A case study of Dongying Sag, Jiyang Depression, Bohai Bay Basin

Taking the Paleogene Shahejie Formation lacustrine shale in Dongying Sag, Jiyang Depression, Bohai Bay Basin, as an example, this paper makes a systematic study on the properties of shale of lower part of Sha-3 Member (Es3x) and upper part of Sha-4 Member (Es4s), including porosity, compressibility, mechanical properties, oil saturation, gas-oil ratio and oil saturation pressure by lab analysis and well log data of shale cores taken from different depths. On this basis, the movability of shale oil is discussed in terms of formation energy. According to the study results, both the elastic movable oil ratios and the solution gas driving movable oil ratios of Es3x and Es4s increase with the shale burial depth increasing, and both ratios of Es4s are generally higher than that of Es3x at the same depth. Within the depth of 2 800 – 4 000 m, the total movable oil ratio of Es3x varies from 8% to 28%, while the total movable oil ratio of Es4s varies from 9% to 30%. Combining with the profiles of oil saturation and movable oil ratio of shale, a conclusion is made that the shale of Es3x and Es4s deeper than 3 400 m in the study area are favorable objects for shale oil exploration. Key words: lacustrine shale, shale oil, movable oil, porosity, compressibility, saturation pressur

Formation fluid characteristics and hydrocarbon accumulation in the Dongying sag, Shengli Oilfield

Based on the analysis of geochemical characteristics and distribution of different formation waters, a new origin identification standard was established for the formation water in the Paleogene Shahejie Formation in the Dongying Sag. The migration paths of the connate water expelled from source rocks are similar to those of the hydrocarbons coming from the same rocks, so the geochemical characteristics of the connate water coming from the source rocks can be used as auxiliary indexes to study hydrocarbon migration. Considering fluid pressure and formation water distribution, the Paleogene fluids are divided into three fluid systems: normal-pressure open fluid system, overpressure confined fluid system, and transition fluid system. The differences in hydrocarbon-bearing fluid characteristics, hydrocarbon migration dynamic, hydrocarbon-bearing fluid flow type between these fluid systems were studied. According to characteristics of the hydrocarbon-bearing fluid charging into traps, and formation water drainage pattern, three typical oil accumulation models were classified. In the overpressure confined fluid system, the main oil accumulation mode is high oil saturation fluid entering traps and displacing formation water, and “continuous” reservoirs are prone to form, and fluid oil saturation, fluid charging pressure and fluid seeping conditions affect reservoirs’ oil accumulation extent. In the normal-pressure open fluid system, the main oil accumulation modes include low oil saturation fluids enter a trap while formation water is overflowing out of the trap, and low oil saturation fluids enter a trap while formation water is seeping out of the trap. The amount of hydrocarbon-bearing fluid, fluid oil saturation, trap height, and caprock sealing ability affect reservoir's oil accumulation extent. Key words: formation fluid system, hydrocarbon-bearing fluid, formation water, connate water, non-Darcy flow, hydrocarbon accumulation mode

Toxicity profile characteristics of novel androgen-deprivation therapy agents in patients with prostate cancer: a meta-analysis

<p><b>Background</b>: To investigate the toxicity profile characteristics of abiraterone acetate and enzalutamide to see if they are of critical clinical value.</p> <p><b>Methods</b>: Prospective studies were identified by searching the PubMed, EMBASE, Cochrane Library, and American Society of Clinical Oncology Meeting abstracts. Randomized clinical trials that evaluate abiraterone acetate or enzalutamide in patients with prostate cancer were included. The risk ratio (RR) of adverse events (AEs) was calculated for each trial along with appropriate 95% CI using fixed- or random-effects methods.</p> <p><b>Results</b>: Ten studies (5 abiraterone acetate, and 5 enzalutamide studies) were included in the meta-analysis. Use of abiraterone acetate was associated with an increased risk of all-grade adverse effects (RR = 1.01, 95% CI: 1.01–1.02) and high-grade adverse effects (RR = 1.29, 95% CI: 1.15–1.45). Also, there was a significantly higher incidence of some individual adverse effects (e.g. liver-function test abnormalities, arthralgia, cardiac adverse effects, diarrhea, oedema, hypertension and hypokalemia). Treatment with enzalutamide did not increase the risk of all-grade adverse effects and high-grade adverse effects, but there was a significantly higher incidence of some individual adverse effects (e.g. back pain, fatigue, hot flush and hypertension).</p> <p><b>Conclusions</b>: Both abiraterone acetate and enzalutamide have toxicity profile characteristics that need to be recognized. Understanding the toxicity profile characteristics of both drugs could promote decision making in clinical use.</p

The need for integrating family planning and postabortion care in China

Objective: To assess the need for integrating postabortion care with family planning services in China. Method: We collected data from a clinic-based study of 24 abortion clinics in 3 large cities in China. Results: There was a total of 287 (10.3%) high-risk abortions among the 2780 respondents, 974 (35%) of whom had had repeated abortions and 48.4% had had 2 abortions within 1 year; 63.7% of the current pregnancies resulted from not using contraceptives; 28.8% and 19.8% of these new pregnancies, respectively, were due to the failure of the rhythm or the withdrawal method; only 9.7% of the respondents consistently used condoms; and only 9.1% could identify the correct time of their first ovulation following an abortion. Conclusion: Contraceptive neglect and the high rates of repeated and high-risk abortions call for the integration of postabortion care with family planning services in China