| Based on drilling records, physical tests, oil and gas geochemical tests, well logging and seismic data, as well as multidisciplinary theories and methods in volcanic geology, seismic volcano-stratigraphy and petroleum geology, this dissertation covers the comprehensive studies volcanic reservoir characterization and hydrocarbon accumulation regulation. The study mainly includes four parts:geologic and geophysical identification of volcanic reservoir, seismic characterization and distribution of volcanic facies, physical and heterogeneity properties of volcanic facies and hydrocarbon accumulation regulation. Geologic and geophysical identification of volcanic reservoir includes the identification and characterization of volcanic lithology and volcanic facies, volcanic-logging facies and volcanic-seismic facies based on drilling, logging as well as seismic data. Seismic identification and distribution of volcanic facies:based on the volcanic stratigraphic interface, the volcanic stratigraphic framework of Cenozoic volcanic rocks in the Eastern sag of Liaohe Basin has been built. Under the defined stratigraphic framework, the volcanic facies are identified by using the drilling data-constrained seismic mapping method for intermediate-basic volcanic facies, and the volcanic facies distribution within volcanic bodies is shown in the map. Physical and heterogeneity properties of volcanic facies:based on volcanic diagenesis, reservoir space and reservoir physical property analysis, the physical and heterogeneity establishments of the different volcanic facies and sub-facies from the study of combination pattern on various kinds of volcanic rocks within each facies or sub-facies. Hydrocarbon accumulation regulation is after the condition study of "source, reservoir and cap rocks", and is the hydrocarbon accumulation factor analysis of strike-slip fault reconstructed multi-layer intermediate-basic volcanic rock, from both sag and block scales. The volcanic rock hydrocarbon accumulation pattern can be summarized by the research of "source, reservoir and cap rock" special and temporal relationships, volcanic reservoir heterogeneity, attitude of stratum and lateral blocking types in the Eastern sag of Liaohe Basin.1. Geologic and geophysical identification of volcanic rocks in the Eastern sag of Liaohe BasinDetailed mineralogy, texture and structure descriptions of 4 categories 11 sub-categories and 5 facies 14 sub-facies volcanic rocks from the Eastern sag of Liaohe Basin were conducted by core and thin section observations in this dissertation, as well as the summary of geological and geophysical identification marks.Logging facies of volcanic conduit and explosive, effusive, extrusive, volcanic seimentary facies were identified by using conventional well logging curves, among which the compound lava flow subfacies, tabular lava flow subfacies, hyaloclastic subfacies, outerclastic volcanic deposit subfacies and re-transported subfacies can be further recognized. The details are as follows:(1) the explosive facies is generally characterized by box-shaped or microjugged-straight curve of low RLLD, low-medium CNL, low-medium DEN and medium DT, and the contact relationship of both the top and the bottom are mostly abrupt contact; (2) compound flow sub-facies generally showed jugged amplitude high-medium RLLD, CNL, DEN and DT; (3) tabular sub-facies generally has bell-shaped medium-high RLLD, low-medium CNL, high DEN, low-medium DT, with gradational contact on the top and abrupt contact at the bottom; (4) hyaloclastite sub-facies has typical box or gradual jugged shaped low RLLD, high CNL, low-medium DEN and medium DT, with an abrupt contact at both the top and bottom, and are quite thick; (5) extrusive facies typically has bell-shaped medium-high RLLD, low CNL, medium DEN, low-medium DT, with gradational contact at the top and abrupt contact at the bottom.7 volcanic facies are identified by the seismic reflection characteristics from drilling, of which the volcanic diatreme, subvolcanic, pyroclastic flow, hyaloclastite and plate/compound lava sub facies can be recognized. Key corresponds between volcanic facies and seismic characteristics are as follows:①Diatreme sub-facies:the characters of diatreme sub-facies are lumpy or pipe shape (aspect ratio is middle-high) with chaotic seismic reflection configuration, middle-low amplitude, middle-low frequency and middle-bad continuum reflection; ② Subvolcanic sub-facies:the characters of subvolcanic sub-facies are platy or lentoid (aspect ratio is low) with parallel-subparallel seismic reflection configuration, high amplitude, middle-high frequency and middle-good continuum reflection; ③Extrusive facies:the characters of extrusive facies are lentoid or mound shape (aspect ratio is middle) with wavy or disordered seismic reflection configuration, middle-low amplitude, middle-low frequency, middle-continuum reflection; ④Explosive facies:the characters of explosive facies are platy/sill or wedge-like shape (aspect ratio is low) with parallel-subparallel seismic reflection configuration, middle-high amplitude, middle-high frequency and good continuum reflection; ⑤Hyaloclastite sub-facies: the characters of hyaloclastite sub-facies are filling structure (aspect ratio is low-middle) with disordered or wavy seismic reflection configuration, middle-low amplitude, middle-low frequency and middle-bad continuum reflection; ⑥ Tabular/composite lava sub-facies:the characters of tabular/composite lava sub-facies are sill-like shape (aspect ratio is low) with parallel-subparallel seismic reflection configuration, high amplitude, middle-high frequency and good continuum reflection; ⑦Volcanogenic sedimentary facies:the characters of volcanogenic sedimentary facies are sill-like shape (aspect ratio is low) with parallel-subparallel seismic reflection configuration, middle-high amplitude, middle-high frequency and middle-good continuum reflection. Genesis as to why seismic reflections correspond to lithological association and volcanic architecture are discussed in detail. The modal described in this paper is used in subsurface mapping of the volcanic reservoirs and have been proved effective by drilling exploitation. Thus, it is also be useful for mafic volcanic reservoir research in other related areas.2. Seismic identification and distribution of volcanic facies in the Eastern sag of Liaohe BasinCenozoic volcanic strata in the Liaohe Basin can be divided into 4 cycles and 15 stages by identifying the interfaces inside the volcanic strata. The 1st cycle at the bottom and the 4th cycle at the top are composed of basalts, which indicates that the Cenozoic volcanic activities began and ended with mafic magmas. The Cenozoic volcanic formation is dominated in the 2nd and 3rd cycle, and these two cycles show the same lithologic sequence from basalt to trachyte to basalt. The distribution of volcanic rocks is controlled by major faults of northeast orientations, and the maximum thickness of volcanic rocks is mainly along the fault zone. Volcanic rocks from early stages (stage 1-2) were widely spread in the whole sag, while the basalts from the final stages (stage3-15) showed the migration from north to south. The center of volcanic thickness migrated from north and south to center area in Liaohe basin during stage 1-7, and then migrated from center area to south during stage 7-15.Favorable prospecting facies are revealed through comprehensive studies of geology, well logging and seismic data from single and multiple wells following the seismic volcano stratigraphy principle by identifying three volcanic interface levels (stages' edifices' lithofacies) of an intermediate-basic volcanic formation. According to stage interfaces, one or more volcanic edifice-seismic facies containing volcanic facies-seismic facies were identified in each volcanic stage. Based on single well points, volcanic edifice-facies distribution pattern can be described by crossing-well sections. Meanwhile, volcanic bodies can be described by extracting coherent seismic attributes (superimposed volcanic edifices) using volcanic stages as units as well as volcanic edifices and lithofacies through extracting waveform classification properties to establish the relationship between volcanic facies and seismic facies in drilled wells, seismic cross sections and mappings.Identification and processing of seismic data in volcanic facies can be summarized in five steps:1) Identification of volcanic interfaces (stages and facies) in drilled wells; 2) Single well volcanic interface (stages and facies) seismic calibration on seismic crossing-sections and establishment of mutual relationships between geological and seismic data; 3) Comparison of volcanic interfaces (stages and facies) of multiple adjacent wells; 4) Establishment of a distribution model of volcanic edifices and facies in the Hongxing area based on the identification of the three volcanic interfaces (stages>edifices>facies) in volcanic layers revealed by seismic cross sections; 5) Identification of volcanic bodies (superimposed volcanic edifices) by extracting coherent seismic attributes using volcanic stages as units based on volcanic interfaces of single-well and well-tie seismic sections. Then, we identified volcanic edifices and volcanic facies by extracting waveform classification properties. Volcanic facies mapping was completed, constituting the relationship between the volcanic facies and the seismic facies in drilled wells, seismic cross sections and mappings.Based on the analytical results of the volcanic bodies in the Hongxing-Xiaolongwan area, the distribution pattern of volcanic facies in the Eastern sag of Liaohe basin is analysed, and S3q1, S3q2, S3q3, S3q4 and S3q5 volcanic rocks were developed during the main development stages of the fault subsidence. The main patterns are as follows:S3q1、S3q5 are mainly controlled by Jiazhangsi fault, S3q2、 S3q3、S3q4 by Jiazhangsi and Jiadong faults; S3q1、S3q5 are mainly erupted along the fissure, S3q3 is mainly central erupted, and S3q2, S3q4 are both central and fissure erupted; S3q2 is the thickest with thousands of meters thickness, S3q3、S3q4、S3q5 have medium thickness and S3ql being the thinnest; the facies pattern of S3q1、S3q5 is volcanic conduit facies'effusive facies'volcanogenic sedimentary facies, S3q2、 S3q4 volcanic conduit facies ('explosive facies) 'effusive facies'volcanogenic sedimentary facies and S3q3 volcanic conduit facies ('explosive facies) 'extrusive facies ('effusive facies) 'volcanogenic sedimentary facies.3. Reservoir physical properties and heterogeneity of volcanic facies in the Eastern sag of Liaohe BasinThe volcanic rocks in the Eastern sag of Liaohe Basin can be divided into condensed and consolidated diagenesis and compaction diagenesis according to the early diagenesis, of which the condensed and consolidated diagenesis could further be affected by volatilization release, condensing constriction, quenching effect, devitrification, phenocryst burst effect, quasi-syngenetic hydrothermal sedimentation and welding effects; compaction and consolidation diagenesis includes compaction and cementation. It sums up 8 types of diagenesis in total. Among 8 types of diagenesis, volatile release, condensing constriction, quenching effect, devitrification, phenocryst burst effect are beneficial for the formation of the primary porosity reservoirs. Late period of diagenesis include 6 types, among them, dissolution effect, tectonic effect, cryptoexplosive brecciation can improve primary reservoir space, while filling effect, cementation and compaction will lower the primary reservoir space.By observing cores and thin sections,6 categories and 11 subcategories of primary reservoir space in volcanic rocks are identified in the Eastern sag of Liaohe Basin, respectively are vesicular opening (vesicular opening, apricot kernel inner pores), contraction pores (devitrification pores, apricot kernel inner contraction pores), contraction fissure (net contraction fissure, horizontal joints, columnar joints), cleavage fissure, cracks fissure and frame pores (intergranular pores).5 categories and 11 subcategories of secondary reservoir space in volcanic rocks can be identified in this area, respectively are dissolution pores (intragranular dissolved pores, intergranular dissolved pores, interstitial material dissolution pores), dissolved fracture (cleavage dissolved fracture, contraction dissolved fracture, dissolved cracked fracture, dissolved crypto-explosive fracture, dissolved tectonic fracture), tectonic fracture, crypto-explosion fracture and pressure solution fracture.In this dissertation,10 kinds of lithology in the Eastern sag of Liaohe Basin are conducted reservoir studies, showing that vesicular basalt, brecciated basalt, brecciated trachyte, volcanic agglomerate, volcanic breccia, sed-volcanic breccia, tuffaceous sandstone have better reservoir quality; tuff reservoir is moderate; dense basalt, compact trachyte reservoir is poor.Furthermore,5 facies and 13 sub-facies are conducted reservoir heterogeneity study in the Eastern sag of Liaohe Basin, research shows that lithological composition usually consists of a single-phase sub-facies, longitudinal and lateral heterogeneity is weak, such as the volcanic diatreme sub-facies, pyroclastic flows sub-facies, hyaloclastite sub-facies, with overall good physical properties; composed of a single layer distribution of lithological composition subfacies or facies, vertical heterogeneity moderate and lateral heterogeneities weak, such as fall deposits subfacies, surge sub-facies, resedimented volcaniclastics and epiclast-bearing volcanogenic deposits sub-facies, the overall physical medium; a variety of physical properties quite different lithological composition of a single layer distribution subfacies or facies, vertical heterogeneity strong and lateral heterogeneities weak, such as tabular flows sub-facies, extrusive facies, the overall physical medium; from a variety of physical properties quite different lithologies spatially distributed alternately composed of sub-facies, longitudinal and lateral heterogeneity strong compound lava flows sub-facies, the overall poor physical properties; crypto-explosive breccia subfacies heterogeneity controlled by the original rock.4. Hydrocarbon accumulation regulation of volcanic rocks in the Eastern sag of Liaohe BasinBy studying of the oil and the sources correlation, the oil and gas volcanic reservoirs of Hongxing-Xiaolongwan area are from the source rocks located in west of the strike-slip faults (Jiazhangsi fault). From sag scale, as the research object, through tectonic evolution of the Eastern sag of Liaohe Basin analysis, special-temporal relationship research of "sources, reservoirs and caps" shown that the Eastern sag of Liaohe Basin volcanic and sedimentary strata (3rd member of Shahejie formation) which is formed in the period of fault subsidence is transformed by strike-slip later period of fault subsidence (mainly Dongying formation), volcanic and sedimentary strata along strike-slip faults in the plane of the side during the match in Dongying formation, formed a lateral side of the main reservoir and source rocks forming pattern of hydrocarbon accumulation in volcanic reservoirsFrom the block scale, the volcanic bodies as the research object, through volcanic bodies and source rocks longitudinal matching relationship and volcanic facies longitudinal heterogeneity, this dissertation studied the longitudinal oil and gas distribution. In space-time, source, reservoir and cap rocks relations matching premise, volcanic bodies and source rocks longitudinal matching relation with oil and gas: source rocks direct matches reservoir and the cap, the best arrangement relationship, the best source of oil supply; source rocks located in the lower part of reservoir and the cap, the arrangement relationship good, moderate oil supply source; source rocks is located in the upper part of reservoir and cap, the worst arrangement relationship, oil source is not supplied. Volcanic reservoir vertical heterogeneity:The 3rd member of Shahejie formation three stages reservoir and cap distribution patterns as follows, S3q3 reservoir bottom-up followed by pyroclastic flow, outer zone+intermediate zone, intermediate zone+outer zone+resedimented volcaniclastics or epiclast-bearing volcanogenic deposits sub-facies, and the inner zone is mainly in the cap rock band; S3q4 and S3q5 reservoir bottom-up followed by pyroclastic flow+ tabular lava flow bottom boundary, tabular lava flow within flow unit top and bottom interface, tabular lava flow top boundary+compound lava flow bottom boundary, compound lava flow top boundary+resedimented volcaniclastics or epiclast-bearing volcanogenic deposits sub-facies; inner cap bottom-up followed by the inner tabular flow internal unit (between the top and bottom flow unit interface), compound lava flow inside (between the top and bottom interface).From block scale, with volcanic rock as the research object, through formation occurrence and volcanic reservoirs lateral heterogeneity, this dissertation studied lateral distribution of oil and gas research. Source, reservoir and cap rocks space relations match under the premise of stratum:the main points of stratum formation tendency and formation dip two aspects of reservoir control, ground control action tends to reflect the occurrence in the east-dipping strata hinder overall hydrocarbon migration, west-dipping strata stratigraphic occurrence contribute overall hydrocarbon migration; dip control role is reflected in the greater east-dipping strata dip less hydrocarbon migration distance, the greater the west-dipping strata dip hydrocarbon migration distance increases. In addition, the drilling of stratum as the distance from the source rocks smaller control on hydrocarbon of gradually smaller when the distance is less than about lkm, formation occurrence cannot affected hydrocarbon accumulation. Volcanic lateral reservoir heterogeneity:volcanic facies lateral heterogeneity weaker, the greater distance lateral migration of oil and gas, volcanic facies heterogeneity is stronger, the smaller distance lateral migration of oil and gas.From block scale, with volcanic rock as the research object, this dissertation studied the hydrocarbon reservoir types through the formation occurence and occurrence of lateral sealed type. Hongxing-Xiaolongwan volcanic bodies of stratum can be divided into east-dipping strata, west-dipping strata and nearly horizontal strata due to the different formation occurrence, so the causes of different traps are also different sealed types, thereby forming structural hydrocarbon reservoir, lithological hydrocarbon reservoir and structural-lithological hydrocarbon reservoir three kinds of reservoir type. Structural hydrocarbon reservoirs are mainly distributed in Hongxing volcanic bodies which is east-dipping strata, lithological hydrocarbon reservoirs are mainly distributed in the formation occurrence nearly horizontal or low-angle west-dipping strata at the transition between the Hongxing and Xiaolongwan volcanic bodies, structural-lithological hydrocarbon reservoirs are mainly distributed in the formation occurrence at a high angle of the main west-dipping Xiaolongwan volcanic bodies. |
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