TOF-SIMS Study of the Hydrocarbon-generating Potential of Mineral-Bituminous Groundmass

The TOF-SIMS fragment peak ascription of organic and inorganic ions of mineral-bituminous groundmass of Jurassic source rocks in the Turpan-Hami and Junggar basins was studied by using the high-resolution Time of Flight Secondary Ion Mass Spectrometer (TOF-SIMS). The characteristics of spectrum distribution and constitution of fragment ions of the mineral-bituminous groundmass are discussed; then the methods of evaluating its hydrocarbon-generating potential are developed. In addition, the typical parameters, XAL, Yox and ZAR, for indicating the hydrocarbon-generating potential of mineral-bituminous and other organic matter in source rocks are put forward to reflect the aliphatic, oxygenous, and aromatic structures. It is confirmed by Rock-Eval that these parameters are significant in evaluating hydrocarbon generation. Moreover, the detection of the nitrogenous and oxygenous fragment ion, CH5NO3+, in the mudstone formed in semi-deep lakes and in the carbargilite formed in the arms of lakes reflects

Organic Petrologic Characteristicsand Hydrocarbon-Generating Significance of Epiphyton

The Epiphyton occurred in the carbonate rock of lower Paleozoic in North China was analyzed by using the optical and some micro-area methods such as Micro-FT-IR and TOF-SIMS. The result shows that tbe Epiphyton belonging to the calcic algae has a certain hydrocarbon-generating potential and the hydrocarbou-generating action may continue to the high mature stage.

Modeling of the whole hydrocarbon-generating process of sapropelic source rock

Based on experimental data from hydrocarbon generation with a semi-open system, hydrocarbon generation kinetics modeling in gold tube of closed system, high temperature pyrolysis chromatography mass spectrometry experiment with open system and geological data, the characteristics of whole hydrocarbon-generating process, hydrocarbon expulsion efficiency and retained hydrocarbon quantity, origins of natural gas generated in high-over mature stage and cracking temperature of methane homologs were investigated in this study. The sapropelic source rock has a hydrocarbon expulsion efficiency of 30%-60% and 60%-80% in the major oil generation window(with Ro of 0.8%-1.3%) and high maturity stage(with Ro of 1.3%-2.0%) respectively; and the contribution ratio of kerogen degradation gas to oil cracking gas in total generated gas in high maturity stage is about 1:4. The degradation gas of kerogen accounts for 20%, the retained liquid hydrocarbon cracking gas accounts for 13.5%, and the amount of out-reservoir oil cracking gas(including aggregation type and dispersed oil cracking gas) accounts for 66.5%. The lower limit of gas cracking is determined preliminarily. Based on the new understandings, a model of the whole hydrocarbon-generating process of source rock is built.

A new method to reconstruct hydrocarbon-generating histories of source rocks in a petroleum-bearing basin——the method of geological and geochemical sections

Via investigating typical Palaeozoic and Mesozoic petroleum-bearing basins in China by using thermal maturation theories of organic matter to improve the conventional Karweil’s method, a new method to reconstruct hydrocarbon-generating histories of source rocks has been suggested. This method, combining geological background with geochemical information makes the calculated VRo closer to the measured one. Moreover, it enables us to make clear the hydrocarbon generation trend of source rocks during geological history. The method has the merits of simple calculation and objective presentation, especially suitable to basins whose sedimentation and tectonic movements are complicated.

Pore evolution in hydrocarbon-generation simulation of organic matter-rich muddy shale

For exploration and potential evaluation of deep shale reservoirs with high maturity,hydrocarbon generation and pore evolution of muddy shale in deep high evolution stage were investigated by the high-temperature high-pressure simulation experiment.Results indicated that under high pressure condition,nano-scale micropores in organic matter-rich muddy shale constantly increased as rise of temperature and pressure,leading to increase of shale porosity.However,in the high mature-overmature stage,shale porosity decreased with further increase of temperature and pressure.In contrast to micropores,micro-scale capillary pores and megapores in shale constantly decreased as rise of simulation temperature or pressure,indicating that deep-burial reservoirs was not favorable for free-gas storage;but significant increase of micropores and surface area during this stage could make up for a loss of adsorbed natural gas in shale due to decrease of adsorption capacity which was induced by increase of temperature and pressure,thus leading to high shale gas potential in deep layers.A large number of secondary micropores were developed in the simulated samples such as pyrite and dolomite,demonstrating that shale clasts and mineral matrix could also form abundant secondary micropores during the deep evolution stage;during the evolution process,shale as hydrocarbon source rock could generate a large amount of acidic fluid which was favorable for development of secondary porosity.

Shale pore characteristics of Shahejie Formation: Implication for pore evolution of shale oil reservoirs in Dongying sag, north China

The pore characteristics of shale reservoirs in the lower submember of Member 3 to upper submember of Member 4 of Shahejie Formation in Dongying sag are analyzed,influences of mineral content and organic matter content on porosity and pore size are also investigated,and through the diagenetic thermal simulation experiment,the main pore evolution is further discussed.The results show that the pore structure of shale reservoirs is complex,the micron-nanometer pores can storage liquid hydrocarbons,and the free-phase crude oil is mainly distributed in intergranular dissolution pores of calcite,recrystallized intergranular pores,intergranular shrinkage fractures of clay mineral which have large pore size.Framework minerals and organic matter content directly influence porosity and pore size of shale reservoirs,relationship between porosity and content of felsic mineral as well as content of organic matter content is linear and positive,while relationship between content of carbonated mineral is negative.At the buried depth from 2500 to 3500 m,concentration of organic acid from hydrocarbon generation and expulsion of organic matter,increasing range of pressure coefficient,are well corresponding to highporosity intervals;pore formation in shale oil reservoirs are almost controlled by diagenetic evolution of clay minerals;framework storage spaces formed by carbonate grain crystals as well as intergranular and intergranular dissolution pores of carbonate increases porosity of shale oil reservoirs;local increase of porosity at the depth of 3500e3800 m is mainly caused by coupling of hydrocarbon-generating overpressure and dissolution,and size,distribution and connectivity of pores are enhanced obviously.