Dai Ta-gen

Subtle traps prediction using sequence stratigraphy and 3D seismic technology: A case study from Qikou depression in Huanghua basin °

Forecasting subtle traps by sequence stratigraphy and 3D seismic data is a sensitive topic in hydrocarbon exploration. Research on subtle traps by geophysical data is the most popular and difficult. Based on the sufficiently drilling data, log data, core data and 3D seismic data, sediment sequence of Qikou depression, Huanghua basin was partitioned by using sequence stratigraphy theory. Each sediment sequence system mode was built. Sediment faces of subtle traps were pointed out. Dominating factors forming subtle traps were analyzed. Sandstone seismic rock physics and its response were studied in Tertiary System. Sandstone geophysical response and elastic modulus vary laws with pressure, temperature, porosity, depth were built. Experimental result and practice shows that it is possible using seismic information forecasting subtle traps. Integrated using geology, log, drilling data, special seismic processing technique, interpretation technique, high precision horizon calibration technique, 3D seismic visualizing interpretation, seismic coherence analysis, attribute analysis, logging-constrained inversion, time frequency analysis, subtle traps object is identified and interpreted. Finally, advantage object of subtle trap in this area was determined. Bottomland sand stratigraphic and lithologic reservoirs in Qinan slope zone have been founded by means of high resolution 3D seismic data field technique, high resolution 3D seismic data processing technique and seismic wave impedence inversion technique.

Petrochemical Characteristics of the Mesozoic-Cenozoic Volcanic Rock in Huanghua Basin

Based on the data from typical core sampling, combined with K-Ar dating, petrochemistry, trace elemental geochemistry and isotopic compositions of the Mesozoic-Cenozoic volcanic rock in the Huanghua basin, Bohai region, the geochemical features of the volcanic rock were studied. The rocks fall into four groups: Cenozoic basalt, Mesozoic late Cretaceous basaltic-trachyandesite, Mesozoic late Cretaceous trachy-dacite and liparite, and Mesozoic early Triassic dacite. The distribution pattern of the main elemental abundance of late Mesozoic shows a typical bimodal. Chronologically, for the volcanic rock, the amount of SiO2 decreases gradually, the contents of Fe2O3,FeO,CaO,MgO,TiO2,P2O5 and MnO increase little by little. The Cenozoic basalt is derived from the asthenospheric mantle. The late Cretaceous basaltic-trachy-andesite is derived from the enriched lithospheric mantle. In late Cretaceous and early Palaeogene, the felsic volcanic rock may be derived from fractional melting of the crust.

Geochemical evidences of metallogenic materials’ source in Xiong’ershan Au-Ag orefield, Henan

The H. O. S isotopic geochemical features and the REE geochemical parameters of some deposits in Xiong’ershan region are discussed, and the coherent various geological bodies are confirmed.

The Physico-Chemical Conditions for Mobilization of Gold in Mobin Gold Deposit,Southwest Hunan, China

Experiments on water-rock interaction were carried out on wall-rock samples from the Mobin gold deposit, Southwest Hunan, China, with the aim of determining the optimum physical and chemical conditions for the mobilization of gold in solution. Results indicate that gold is most easily mobilized from the wall rock-tuffaceous slate of the Mobin Deposit. Mobilization is optimized if fluids are neutral to slightly alkaline and contain both chlorine and sulphur ions at the concentration and composition of about [0.25M (NH4)2S+ 1M NaCl]. The amount of gold leached from the tuffaceous slate increases with temperature although the effect decreases above about 200°C.