Logging curves characteristics and response mechanisms of basaltic facies and sub-facies: A case study from eastern sag of Liaohe depression, Northeast China

Based on five types of conventional logging curves including GR,RLLD,CNL,DEN and AC,and 39 core samples from 30 representative boreholes,the logging characteristics and lithofacies and sub-facies of the basaltic rocks were studied.Three basaltic facies and four sub-facies are recognized from the well logs,includ-ing volcanic conduit facies(post intrusive sub-facies),explosive facies,and effusive lava flow facies(tabular flow,compound flow and hyaloclastite sub-facies).The post intrusive,tabular flow and compound flow sub-facies logging curves are mainly controlled by the distribution of vesiculate zones and vesiculate content,which are characterized by four curves with good correlation.Post intrusive sub-facies are characterized by high RLLD,high DEN,with a micro-dentate logging curve pattern,abrupt contact relationships at the top and base.Tabular flow sub-facies are characterized by high RLLD,high DEN,with a bell-shaped log curve pattern,abrupt contact at the base and gradational contact at the top.Compound flow sub-facies are characterized by medium-low RLLD,with a micro-dentate or finger-like logging curve pattern,abrupt contact at the base and gradational contact at the top.Explosive facies and hyaloclastite sub-facies logging curves are mainly controlled by the distribution of the size and sorting of rock particles,which can be recognized by four kinds of logging curves with poor cor-relation.Explosive facies are characterized by low RLLD,medium-low CNL and low DEN,with a micro-dentate logging curve pattern.Hyaloclastite sub-facies are characterized by low RLLD,high CNL,low DEN and high AC,with a micro-dentate logging curve pattern.The present research is beneficial for the prediction of basaltic reser-voirs not only in the Liaohe depression but also in the other volcanic-sedimentary basins.

Quantitative effect of kerogen type on the hydrocarbon generation potential of Paleogene lacustrine source rocks,Liaohe Western Depression,China

Kerogen types exert a decisive effect on the onset and capacity of hydrocarbon generation of source rocks.Lacustrine source rocks in the Liaohe Western Depression are characterized by thick deposition,high total organic carbon(TOC)content,various kerogen types,and a wide range of thermal maturity.Consequently,their hydrocarbon generation potential and resource estimation can be misinterpreted.In this study,geochemical tests,numerical analysis,hydrocarbon generation kinetics,and basin modeling were integrated to investigate the differential effects of kerogen types on the hydrocarbon generation potential of lacustrine source rocks.Optimized hydrocarbon generation and expulsion(HGE)models of different kerogen types were established quantitatively upon abundant Rock-Eval/TOC/vitrinite reflectance(R_(o))datasets.Three sets of good-excellent source rocks deposited in the fourth(Es4),third(Es3),and first(Es1)members of Paleogene Shahejie Formation,are predominantly types I-II_(1),II_(1)-II_(2),and II-III,respectively.The activation energy of types I-II_(2)kerogen is concentrated(180-230 kcal/mol),whereas that of type III kerogen is widely distributed(150-280 kcal/mol).The original hydrocarbon generation potentials of types I,II_(1),II_(2),and III kerogens are 790,510,270,and 85 mg/g TOC,respectively.The Ro values of the hydrocarbon generation threshold for type I-III source rocks gradually increase from 0.42%to 0.74%,and Ro values of the hydrocarbon expulsion threshold increase from 0.49%to 0.87%.Types I and II_(1)source rocks are characterized by earlier hydrocarbon generation,more rapid hydrocarbon expulsion,and narrower hydrocarbon generation windows than types II_(2)and III source rocks.The kerogen types also affect the HGE history and resource potential.Three types(conventional,tight,and shale oil/gas)and three levels(realistic,expected,and prospective)of hydrocarbon resources of different members in the Liaohe Western Depression are evaluated.Findings suggest that the Es3 member has considerable conventional and unconventional hydrocarbon resources.This study can quantitatively characterize the hydrocarbon generation potential of source rocks with different kerogen types,and facilitate a quick and accurate assessment of hydrocarbon resources,providing strategies for future oil and gas exploration.

Geothermal Evidence of the Mesozoic and Cenozoic Lithospheric Thinning in the Liaohe Depression

The Liaohe （辽河） depression is an important part of the Bohai （渤海） Bay Basin, and the Bohai Bay Basin located in the center of Hthospheric destruction and thinning in the eastern North China Craton. The North China Hthospheric thinning activities have been verified from evidences of structural geology, petrology, geochemistry and geophysics, but there are still some controversies on their timing, mechanism and controlling factors. The sedimentary basin is a thin-bedded geologic unit with a limited distribution in the upper lithosphere, and its formation and evolution represent the shal- low response of the deep geodynamic process. Therefore, its thermal evolution is closely related to the deep dynamic conditions. In this article, the Mesozoic-Cenozoic thermal history of the Liaohe depres- sion is reconstructed using the vitrinite reflectance and apatite fission track data. Meanwhile ＂thermal＂ ilthospheric thicknesses in the Mesozoic and Cenozoic are calculated using the geothermic method on the basis of the above thermal history results. The results show that the Liaohe depression has undergone the Cretaceous and Paleogene heat flow peaks, 81 and 83 mW/m2, respectively, corres- ponding to two strong rift movements. Accor- dingly, the depression has experienced two dif- ferent levels of thinning processes in the Creta- ceous and the Paleogene since the Mesozoic, and the ＂thermal＂ lithospheric thicknesses were 60 and 50 Ion, respectively. This may reveal that the depression has experienced two large-scale de- structions. The work may provide valuable geo- thermal evidence for initial revealing the time, process and stage of the lithospheric thinning in the Liaohe depression.

Accumulation conditions and key exploration&development technologies of heavy oil in Huanxiling oilfield in Liaohe depression,Bohai Bay Basin

The Huanxiling oilfield is located in the southern part of the western slope of the western sag in Liaohe depression.The west side of this oilfield is connected with two sets of high-quality source rocks of Member 3 and Member 4 of Shahejie Formation in Qingshui sub-sag.The oilfield has fan delta,turbidite fan and other types of reservoirs,it also has cap rock of thick mudstone in Member 3 and Member 4 of Shahejie Formation.Under background of the warped basement,the warped fault-block draped compound trap zone are developed,which includes nine types of trap.From perspective of hydrocarbon accumulation,the slope of this area has always been the target area for hydrocarbon migration and accumulation.Inclusion analysis shows that there are multiple stages of hydrocarbon charging in this area,and the main reservoir forming period is the sedimentary period of Member 3 of Shahejie Formation and the sedimentary period of Dongying Formation.High-quality source-reservoir-cap conditions ensure large-scale hydrocarbon accumulation in this area.Based on the theory of compound hydrocarbon accumulation,many types of oil and gas reservoirs,including light oil reservoir and heavy oil reservoir,have been found in this area,with total reserves of 500 million tons.In view of the oilfield characterized by large reservoir burial span,multiple oil-bearing strata,strong heterogeneity and various types of oils,multi-batch seismic data processing&interpretation technology and thin reservoir inversion technology based on geological model are established in the preliminary exploration period,steam-flooding physical simulation technology of heavy oil,oil-reservoir fine description technology of thermal recovery heavy oil,steam huff and puff technology of ordinary heavy oil and steam-flooding technology of mid-deep buried heavy oil are developed in the development period,and technologies such as separate-layer injection,selective injection,sand control and lifting of heavy oil are matched and improved.These technology series provides technical guarantee for efficient exploration and development of Huanxiling oilfield.

Deformation mechanism and hydrocarbon significance of Eocene organic-rich fine-grained soft sediments in the Leijia Region,Liaohe Depression

The deformation structure of soft sediments has always been a research hotspot,which is of great significance for analyzing the tectonic and sedimentary evolution background of a basin,as well as the physical properties of reservoirs.Previous studies have reported that a large number of soft sediment deformation structures are developed in the western part of Liaohe depression.In this study,through core observation and thin section identification,various types of deformation structures are identified in the core samples which are collected from the upper Es4 in the Leijia region,western sag of Liaohe depression,such as liquefied dikes,liquefied breccia,convoluted laminae,annular bedding,synsedimentary faults,vein structures,etc.Based on the characteristics of core structure,single well profile and continuous well profile,combined with the regional background,this study clarifies that the deformation structure of soft sediments in the study area is mainly caused by seismic action.It is found that the permeability and porosity of deformation layers in the study area are higher than those of the undeformation layers,which proves that the deformation structure of soft sediments has a good effect on improving the physical properties of reservoirs.