渤海湾盆地M区块潜山上覆坡积岩发育控制因素及成因模式

文中以渤海湾盆地M区块潜山油藏为例,建立坡积岩层的发育模式。M区块是一个潜山–披覆背斜构造,储层岩性主要为区域变质的花岗片麻岩,坡积岩层发育在变质岩潜山和沙三段之间。潜山上覆坡积岩层主要为砂岩及泥岩,进一步可划分为坡积砂岩、坡积泥岩。坡积岩的形成控制因素包括构造因素及沉积因素。坡度太大不利于坡积岩的堆积,渤海湾的断裂活动促进了裂缝及节理的形成,并加剧了深部的淋滤作用,其为坡积岩的发育提供了基础物质。坡积物是一套近源堆积物,其分选、磨圆都很差,成分与基岩基本一致。坡积物的堆积过程中几乎没有水流作用,沿坡的重力分量是其主要的搬运动力。

渤海JZ区块变质岩潜山“坡积岩层”岩石特征及工程录井识别方法

渤海JZ区块变质花岗岩潜山界面之上局部发育—套较薄的砂砾岩和砂岩（坡积岩层）。该坡积岩层厚薄分布不均，横向可对比性差，为现场钻井地质作业带来诸多问题。利用岩心、岩屑资料分析坡积岩的岩性特征，可分为长石砂岩和岩屑砂岩2种岩性，表明该坡积岩层应为2种不同成因形成的砂岩。通过分析工程录井参数与地层岩性的响应特征，应用钻井工程参数建立功指数和机械比能模型，结合其他录井手段，实现对潜山坡积岩的随钻实时判别。经过研究区多口井的实际资料处理与验证，随钴识别率高达86.7％，应用效果较好。

Carbon and oxygen isotope characteristics of foraminiferan from northern South China Sea sediments and their significance to late Quaternary hydrate decomposition

Carbon and oxygen isotope and dating analyses of foraminiferan in sediment cores collected from three different areas of the northern slope of the South China Sea were conducted, in order to examine the records of the gas hydrate decomposition events since the late Quaternary under the conditions of methane seepage. The results show that： 1） the δ13C values of the benthic foraminiferan Uvigerina spp. （size range of 0.25-0.35 ram） are from -0.212% to -0.021% and the δ180 values of the planktonic foraminiferan Globigerinoides ruber （size range of 0.25-0.35 ram） are from -0.311% to -0.060%; 2） three cores （ZD2, ZD3 and ZS5） from the bottom of a hole are aged for 11 814, 26 616 and 64 090 a corresponding to the early oxygen isotope stage （MIS） Ⅰ, Ⅲ and Ⅳ final period, respectively; 3） a negative-skewed layer of carbon isotope corresponds to that of MIS II （cold period）, whose degree of negative bias is -0.2%0; and 4） the δ13C compositions of foraminiferans are similar to those of the Blake Ridge and the Gulf of Mexico sediments of the late Quaternary. According to the analysis, the reasons for these results are that the studied area is a typical area of methane seep environment in the area during MIS II due to the global sea-level fall and sea pressure decrease. Gas hydrate is decomposed and released, and a large number of light carbon isotopes of methane are released into the ocean, dissolved to inorganic carbon （DIC） pool and recorded in the foraminiferan shells. A pyrite layer developed in the negative bias layers of the foraminiferans confirms that the δ13C of foraminiferans is more affected by methane and less by the reduction of marine productivity and early diagenesis. The use of foraminiferan δ13C could accurately determine late Quaternary hydrate release events and provide evidence for both reconstructing the geological history of methane release events and exploring natural gas hydrate.

Study on Character of Micro-Canal Deposit and Its Significance in Petroleum Geology——Case study of Tuo-147-well in north zone of Dongying depression

Exploration on reservoir of glutenite segment in steep slope zone of half graben-like basin is one of the hot spot targets at present and in the future for new reservoirs; And the study of sediment character of sandy-conglomerate bodies is the keystone and also the difficult problem. Taking Tuo-147-well area in north zone of Dongying depression as an example, the micro-canal sedimentation was researched. The result shows that many micro-canals exist at the end of slope grain-flow in steep slope zone of half graben-like basin; The micro-canals grow at the end of subaqueous grain-flow deposited bodies of 3rd member of the Shahejie formation. The main condition of micro-canal formation is the slope angle less than 18° and a long suitable sedimentary slope. These micro-canals may communicate the reservoir of glutenite segment in steep slope zone and the hydrocarbon stratum as a bridge role. Therefore, it is significant in theory and practice for discovering a series of micro-canals at the end of slope grain-flow in steep slope zone of half graben-like basin.

A modified Hoek-Brown failure criterion considering the damage to reservoir bank slope rocks under water saturation-dehydration circulation

After water is impounded in a reservoir, rock mass in the hydro-fluctuation belt of the reservoir bank slope is subject to water saturation- dehydration circulation （WSDC）. To quantify the rate of change of rock mechanical properties, samples from the Longtan dam area were measured with uniaxial compression tests after different numbers （1, 5, 10, 15, and 20） of simulated WSDC cycles. Based on the curves derived from these tests, a modified Hock- Brown failure criterion was proposed, in which a new parameter was introduced to model the cumulative damage to rocks after WSDC. A case of an engineering application was analyzed, and the results showed that the modified Hock-Brown failure criterion is useful. Under similar WSDC-influenced engineering and geological conditions, rock mass strength parameters required for analysis and evaluation of rock slope stability can be estimated according to this modified Hoek-Brown failure criterion.