Theory, Technology and Practice of Unconventional Petroleum Geology

0 INTRODUCTION The breakthroughs in unconventional petroleum have a great impact on world petroleum industry and innovation in petroleum geology(Dou et al,2022;Jia,2017;Zou et al.,2015b,2014a;Yerkin,2012;Pollastro,2007;Schmoker,1995).The exploration and development evolution from conventional petroleum to unconventional petroleum and more and more frequent industrial activities of exploring petroleum inside sources kitchen have deepened theoretical understanding of unconventional petroleum geology and promoted technical research and development(Jia et al.,2021,2017;Jin et al.,2021;Zhao W Z et al.,2020;Ma Y S et al.,2018,2012;Zou et al.,2018b,2016,2009;Dai et al.,2012).We have introduced and extended the theory of continuous hydrocarbon accumulation since 2008 and published several papers/books(in Chinese and English)with respect to unconventional petroleum geology since 2009,basically forming the theoretical framework for this discipline(Yang et al.,2022a,2021a,2019a,,2015a;Zou et al.,2019c,2017b,2014a,,2013a).In this paper,we present the background of unconventional petroleum geology,review the latest theoretical and technological progress in unconventional petroleum geology,introduce relevant thinking and practices in China,and explore the pathway of unconventional petroleum revolution and multi-energy coordinated development in super energy basins,hopefully to promote the unconventional petroleum geology and industry development.

Characteristics of Volcanic Reservoirs and Hydrocarbon Accumulation of Carboniferous System in Junggar Basin, China

The Carboniferous volcanic reservoirs in Junggar Basin contain rich hydrocarbon resources,implying a great exploration potential,so that they have become a key replacement target for“three-dimensional exploration”.The study on the Carboniferous volcanic reservoirs and their hydrocarbon accumulation elements is significant for clarifying the orientation for exploration.In this paper,based on 37 reserves reports and 3200 reservoir test data,the Carboniferous volcanic reservoirs in Junggar Basin were discussed from the prospective of lithology and lithofacies,physical properties,reservoir types,main controls on hydrocarbon accumulation,and hydrocarbon accumulation patterns.It is found that the Carboniferous in the basin is mostly in the multi-island ocean-volcanic island arc structural-sedimentary environment,so it is geologically eligible for forming in-situ volcanic reservoirs.The volcanic rocks are:(1)mostly distributed along deep and large faults,with the lithology and lithofacies controlled by volcanic architectures;(2)dominantly lava,followed by volcaniclastic lava and volcaniclastic rock;(3)distributed in the periphery of hydrocarbon-generating sag and within the source rocks horizontally,and concentrated in the weathering crust at the top longitudinally,possibly leading to reworked weathering crust reservoir;and(4)liable to form inner reservoirs.The volcanic reservoirs can be concluded into four hydrocarbon accumulation patterns,i.e.,self-generating&self-storing in paleo-uplift and vertical migration,self-generating&self-storing in paleo-uplift and lateral migration,young-generating&old-storing in fault zone and vertical migration,and young-generating&old-storing in paleo-uplift and lateral migration.Future exploration will focus on the effective source rock development and hydrocarbon supply zones and the selfgenerating&self-storing and young-generating&old-storing patterns.The exploration prospects are determined to be the Ludong-Wucaiwan-Baijiahai slope belt and the southern slope belt of the Shaqi uplift(self-generating&self-storing pattern)in eastern Junggar,and the fault and nasal arch zone at the northwestern margin and the nasal arch zone(deep and large structure)in the Luxi area(younggenerating&old-storing pattern)in western Junggar.

New advances in the assessment of tight oil resource in China

The research on tight oil becomes another hotspot in the field of unconventional oil and gas after the boom of shale gas.The global recoverable resources of tight oil are estimated to be around 47.3×10^(9)t.In recent years,significant progress has been made in the technologies of tight oil exploration and development in North America,thus stimulating the dramatic increase of tight oil production.Meanwhile,China has also acquired remarkable achievements in tight oil exploration.Mature assessment methods have been established for tight oil resources by the US,generally dominated by analogy and statistical methods with their own advantages and disadvantages as well as applicable conditions.In China,improvement of resource evaluation techniques becomes an urgent issue in increasing tight oil reserve and production.This study mainly discusses the resource evaluation methods and resource enrichment characteristics of tight oil.Seven kinds of assessment methods in three categories(i.e.,analogy,statistical and genetic method)and evaluation parameters have been preliminary established,and are specifically applied in the Sichuan,Ordos,Songliao,Junggar,Bohai Bay and other tight oil basins through the newly hierarchical resource abundance analogy method,the estimated ultimate recovery(EUR)analogy method and the small-cell volumetric method.The preliminary evaluation results reveal that China has great potential in tight oil resource,and the geological resources amount to 20×10^(9)t,providing a resource base for large-scale development.

Genomic landscape of mitochondrial DNA insertions in 23 bat genomes:characteristics,loci,phylogeny,and polymorphism

The transfer of mitochondrial DNA to the nuclear genome gives rise to the nuclear DNA sequences of mitochon-drial origin(NUMTs),considered as a driving force in genome evolution.In this study,NUMTs in 23 bat genomes were investigated and compared systematically.The results showed that NUMTs existed in 22 genomes except for Noctilio leporinus,suggesting that mitochondrial fragment insertion in the nuclear genome was a common event in bat genomes.However,remarkable variations in NUMTs number,cumulative length,and proportion in the nu-clear genome were discovered across bat species.Further orthologous NUMT loci analysis of the Phyllostomidae family indicated that the NUMTs insertion events in bat genomes were homoplasy-free.The NUMTs were mainly inserted into the intergenic regions,particularly,co-localized with repetitive sequences(especially transposable el-ements).However,several NUMTs were inserted into genes,some of which were in the exon region of functional genes.One NUMT in the genome of Pteropus alecto surprisingly matched with cDNA of ATP8B3 that provided evidence of NUMTs with coding function.Phylogenic analysis on NUMTs originating from COXI and COXII loci highlighted 2 clusters of Yinpterochiroptera and Yangochiroptera for Chiroptera.Seven NUMTs from Rhinolophus ferrumequinum were amplified,and the sequencing results confirmed the reliability of the NUMT analysis.One of them was polymorphic for the presence or absence of the NUMT insertion,and each genotype of NUMT loci showed a distinct regional distribution pattern.The information obtained in this study provides novel insights into the NUMT organization and features in bat genomes and establishes a basis for further studying of the evolution of bat species.