冀东油田南堡滩海地区油气层损害机理与油气层保护方法研究及应用

Study and Application of Damage Mechanism and Protection Method of reservoir in Nanpu Shallow Beach Sea Area is one of the key research projects of Jidong Oilfield Company of PetroChina Company Limited from 2007 to 2008. Located at Nanpu Sag in Huanghua Depression of Bohaiwan Basin, Nanpu Shallow Beach Sea Area with 1000km2 exploration area posseses three sets, shallow Minghuazhen Formation and Guantao Formation of Upper Tertiary, middle-deep Dongying Formation of Lower Tertiary, deep Ordovician, of oil bearing series, according to the achievement of the connecting 3D seismic structure interpretation and the structural geological comprehensive research. Its main reservoir types include Upper Tertiary structural reservoir, Lower Tertiary structural and lithological-structural reservoir, and Ordovician ancient buried hill reservoir. How to protect reservoir, complete well and lift high efficiently is the key to realize high and stable yield of the oil wells during drilling, completing well, testing and repairing well. It is important for reservoir protecting during drilling that directly relate to efficient exploration. Therefore, beginning with basic characteristics and sensitive analysis of reservoir, study of reservoir damage machinism and analysis of reservoir damage potential factor are emphasized when prediction analysis about three-pressure profiles is carried out. The study both of physical and chemical properties and of the strata of the technology of borehole stabilization and reservoir protecting are outstanding. As the conclusions follow: （1）Based on the laboratory experiment about basalt cores, prediction of three- pressure profiles about 30 wells on No.1 and No.2 structure is practiced. The laws of plane pressure distribution are analyzed. （2）According to the analyses about reservoir feature data and about sensitivity evaluation to damage factor in Nanpu oil field, the scheme of reservoir protecting to the sand reservoir of Guantao Formation and the first section of Dongying Formation is put forward. （3）On basis of the analyses on lithological characteristics, mineral compositions, clay minerals, electrical behavior features, physical and chemical properties of basalt of Guantao formation in No.1 and No.2 structure, instability mechanism of basalt sidewall and technical countermeasures are obtained. （4）Aiming at the characteristics of Ordovician dissolution-pore fracture type carbonate reservoir, the scheme of the reservoir protecting to Ordovician is put forward. Creative study of the film forming and sealing and low invasion reservoir protection drilling fluid are successful. In summary, through the study of reservoir heterogeneity and sensitivity, a set of technology and schemes of reservoir protecting is put forward, which is adaptive during drilling the target bed in the research area and establishes the base for efficient exploration. Significant effect has showed in its application in Nanpu oil field.

班公湖带多不杂超大型富金斑岩铜矿床的成岩成矿年代学、岩石学及高氧化岩浆¬流体-成矿作用

Duobuza copper deposit, newly discovered typical gold-rich porphyry copper deposit with superlarge potential, is located in the Tiegelong Mesozoic tectonic -magmatic arc of the southern edge of Qiangtang block and the northern margin of Bangonghu-Nujiang suture. Quartz diorite porphyrite and grandiorite porphyry, occurred in stock, are the main ore-bearing porphyries. As the emplacement of porphyry stock, a wide range of hydrothermal alteration has developed. Within the framework of the ore district, abundant hydrothermal magnetite developed, and the relationship between precipitation of copper and gold and hydrothermal magnetite seems much close. Correspondingly, a series of veinlets and network veinlets occurred in all alteration zones. Therefore, systematic research on such a superlarge high-grade Duobuza gold-rich porphyry copper deposit can fully revealed the metallogenic characteristics of gold-rich porphyry copper deposits in this region, establish metallogenetic model and prospecting criteria, and has important practical significance on the promotion of regional exploration. In addition, this research on it can enrich metallogenic theory of strong oxidation magma-fluid to gold-rich porphyry copper deposit, and will be helpful to understand the metallogenic characteristics in early of subduction of Gangdese arc stages and its entire evolution history of the Qinghai-Tibet Plateau, the temporal and spatial distribution of ore deposits and their geodynamics settings. Northern ore body of Duobuza copper deposit have been controlled with width (north-south) about 100 ~ 400 m, length (east-west) about 1400 m, dip of 200 °, angle of dip 65 °~ 80 °. And controlled resource amount is of 2.7 million tons Cu with grade 0.94% and 13 tons Au with 0.21g/tAu. Overall features of ore body are large scale, higher grade copper, gold-rich. Ore occurred in the body of granodiotite porphyry and quartz diorite porphyrite and its contact zone with wall rock. Through the detailed mapping and field work studies, some typies of alteration are identificated as follows: albitization, biotititation, sericitization, silication, epidotization, chloritization, carbonatization, illitization, kaolinization and so on. The range of alteration is more than 10km2. Wall alteration zone can be divided into potassic alteration, moderate argillization alteration, argillization, illite-hydromuscovite or propylitization from ore-bearing porphyry center outwards, but phyllic alteration has not well developed and only sericite-quartz veins occurred in local area. Moreover, micro-fracture is development in ore district , and correspondingly a series of veinlets are development as follows: biotite vein (EB type), K-feldspar-biotite-chalcopyrite-quartz vein, magnetite-antinolite-K-feldspar vein, quartz-chalcopyrite-magnetite veins (A-type), quartz-magnetite-biotite-K-feldspar vein, chalcopyrite veinlets in potassic alteration zone; (2) chalcopyrite occurring in the center vein–quartz vein (B type), chalcopyrite veinlets, chalcopyrite-gypsum vein in intermediate argillization alteration; (3) chalcopyrite- pyrite-quartz vein, pyrite-quartz vein, chalcopyrite-gypsum veins, quartz-gypsum- molybdenite-chalcopyrite vein in argillization alteration; (4) gypsum veins, quartz-(molybdenite)-chalcopyrite vein, quartz-pyrite vein, gypsum- chalcopyrite vein, potassium feldspar veinlets, Carbonate veins, quartz-magnetite veins in the wall rock. In short, various veins are very abundant within the framework of the ore district. The results of electronic probe microscopy analysis (EMPA) indicate that Albite (Ab 91.5~99.7%) occurred along the rim of plagioclase phenocryst and fracture, and respresents the earliest stages of alteration. K-feldspar (Or 75.1~96.9%) altered plagioclase phenocryst and matrix or formed secondary potassium feldspar veinlets. Secondary biotite occurred mainly in phenocryst, matrix and veinlets, belong to magnesium-rich biotite formed under the conditions of high-oxidation magma- hydrothermal. Chloritization developed in all alteration zones and alterd iron- magnesium minerals such as biotite and hornblende and then formed chlorite veinlets. As the temperature rises, Si in the tetrahedral site of chlorite decreased, and chlorite component evolved from diabantite to ripiolite. The consistent 280℃~360℃ of formation temperature hinted that chlorite formed on the same temperature range in all alteration zones. However, formation temperature range of chlorite from the gypsum-carbonate-chlorite vein was 190℃~220℃, and it may be the product of the latest stage of hydrothermal activity. The closely relationship between biotite and rutile indicate that most of rutiles are precipitated in the process of biotite alteration and recrystallization. In addition, the V2O3 concentration of rutile from ore body in Duobuza gold-rich porphyry copper deposit is >0.4％, indicate that V concentration in rutile has important significance on marking main ore body of porphyry copper deposit. Apatites from Duobuza deposit all are F-rich. And apatite in the wall rock contained low MnO content and relatively high FeO content, which may due to the basaltic composition of the wall rocks. The MnO in apatite from altered porphyry show a strong positive correlation with FeO. In addition, Cl/F ratio of apatite from wall rock was highest, followed by the potassic alteration zone and potassic alteration zone overprinted by moderate argillization alteration was the lowest. SO2 in Apatite are in the scope of 0 to 0.66%, biotite in the apatite has the highest SO2, followed by the potassic alteration zone, potassic alteration zone overprinted by moderate argillization alteration, and the lowest in the surrounding rocks, which may be caused by the decrease of oxygen fugacity of hydrothermal fluid and S exhaust by sulfide precipitation in potassic alteration. Magnetite in the wall rock have higher Cr2O3 and lower Al2O3 features compared with altered porphyry, this may be due to basalt wall rock generally has high Cr content. And magnetites have higher TiO2 content in potassic alteration than moderate argillization alteration overprinted by potassic alteration, argillization and wall rock, suggested that its formation temperature in potassic alteration was the highest among them. The ore minerals mainly are chalcopyrite and bornite, and Au contents of chalcopyrite, bornite, and pyrite are similar with chalcopyrite slightly higher. The Eu* negative anomaly of disseminated chalcopyrite was relatively lower than chalcopyrite in veinlets. Within a drill hole, the Eu* negative anomaly of disseminated chalcopyrite was gradually larger from bottom to top. Magnetite has the same distribution model, with obvious negative Eu* abnormal, and ΣREE in great changes. The gypsum has the highest ΣREE content and the obvious negative anomaly, and biotite obviously has the Eu* abnormal. Based on the petrographic and geochemical characteristics, five series of magmatic rocks can be broadly classified; they are volcanic rocks of the normal island arc, high-Nb basaltic rocks, adakites, altered porphyry and diorite. The Sr, Nd, Hf isotopes and geochemistry of various series of magmatic rock show that they may be the result of mixing between basic magma and various degrees of acid magma coming from lower crust melted by high temperature basic underplating from partial melting of the subduction sediment melt metasomatic mantle wedge. Furthermore S isotope and Pb isotope of the sulfide, ore-bearing porphyries and volcanic rocks indicated ore-forming source is the mantle wedge metasomatied by subduction sediment melt. Oxygen fugacity of magma estimated by Fe2O3/FeO of whole rock and zircon Ce4+/Ce3+ indicated that the oxidation of basalt-andesitic rocks is higher than ore-forming porphyry, and might imply high-oxidation characteristics of underplated basic magma. Its high oxidative mechanism is likely mantle sources metasomatied by subduction sediment magma, including water and Fe3+. And such high oxidation of basaltic magma is conducive to the mantle of sulfides in the effective access to melt. And the An component of dark part within plagioclase phenocryst zoning belong to bytownite (An 74%), and its may be a result of magma composition changes refreshment by basaltic magma injection. SHRIMP zircon U-Pb and LA-ICP-MS zircon U-Pb geochronology study showed that the intrusions and volcanic rocks from Duobuza porphyry copper deposit belong to early Cretaceous magma series (126~105Ma). The magma evolution series are as follows: the earliest diorite and diorite porphyrite → ore-bearing porphyry and barren grandiorite porphyry →basaltic andesite → diorite porphyrite → andesite → basaltic andesite, and magma component shows a evolution trend from intermediate to intermediate-acid to basic. Based on the field evidences, the formation age of high-Nb basalt may be the latest. The Ar-Ar geochronology of altered secondary biotite, K-feldspar and sericite shows that the main mineralization lasting a interval of about 4 Ma, the duration limit of whole magma-hydrothermal evolution of about 6 Ma, and possibly such a long duration limit may result in the formation of Duobuza super-large copper deposit. Moreover, tectonic diagram and trace element geochemistry of volcanic rocks and diorite from Duobuza porphyry copper deposit confirm that it formed in a continental margin arc environment. Zircon U-Pb age of volcanic rocks and porphyry fall in the range of 105~121Ma, and Duobuza porphyry copper deposit locating in the north of the Bangonghu- Nujiang suture zone, suggested that Neo-Tethys ocean still subducted northward at least early Cretaceous, and its closure time should be later than 105 Ma. Three major inclusion types and ten subtypes are distinguished from quartz phenocrysts and various quartz veins. Vapor generally coexisting with brine inclusions, suggest that fluid boiling may be the main ore-forming mechanism. Raman spectrums of fluid inclusions display that the content of vapor and liquid inclusion mainly contain water, and vapor occasionally contain a little CO2. In addition, the component of liquid inclusions mainly include Cl-, SO42-, Na+, K+, a small amount of Ca2+, F-; and Cl- and Na+ show good correlation. Vapor mainly contains water, a small amount of CO2, CH4 and C2H6 and so on. The daughter minerals identified by Laman spectroscopy and SEM include gypsum, chalcopyrite, halite, sylvite, rutile, potassium feldspar, Fe-Mn-chloride and other minerals, and ore-forming fluid belong to a complex hydrothermal system containing H2O-NaCl-KClFeCl2CaCl2. H and O isotopic analysis of quartz phenocryst, vein quartz, magnetite, chlorite and gypsum from all alteration zones show that the ore-forming fluid of Duobuza gold-rich porphyry copper deposit consisted mainly of magmatic water, without addition of meteric water. Duobuza gold-rich porphyry copper deposit formed by the primary magmatic fluid (600-950C), which has high oxidation, ultra-high salinity and metallogenic element-rich, exsolution direct from the magma, and it is representative of the typical orthomagmatic end member of the porphyry continuum. Moreover, the fluid evolution model of Duobuza gold-rich porphyry copper deposit has been established. Furthermore, two key factors for formation of large Au-rich porphyry copper deposit have been summed up, which are ore-forming fluids earlier separated from magma and high oxidation magma-mineralization fluid system.

济阳坳陷及其南缘奥陶系碳酸盐岩潜山储集性及控制因素

The main research area of this thesis is Jiyang Depression in the Bohaiwan Basin and its southern margin. The object formation is Ordovician carbonate. The research is based on the outcrop observation and measurement of Ordovician carbonate and the drilling data of the oilfield. The internal reservoir characteristics of carbonate buried hill and its distribution were studied by comprehensive methods of sedimentology, reservoir geology and structural geology and technics of cathodoluminescence(CL)3electron microprobe,casting and C O isotope analysis etc. The influence depth of paleokarst facies formed during the Paleozoic is discriminated as 36-84m. The sollution porosity is well developed in paleokarst facies of Ordovician carbonate and is an important type of internal reservoir of buried hill. It may be infered that the fractures may be formed mainly during the Mesozoic and Cenozoic, they were not developed during the early Paleozoic when only micro-fractures might be created. The carbon and oxigen isotope analysis shows that the calcite cements in the fractures of Ordovician carbonate and secondary solution pores were related with meteoric water and three stages of fractures were divided. The reservoir space of Ordovician carbonate are mainly secondary porosity, cavern and fracture. The development of structural fracture was controlled by the lithology and tectonic background. More fractures exist in dolomite than that in limestone. There are also more fractures near the fault and the axis of fold. The development of porous reservoir is mainly controlled by the lithology and diagenesis, especially dolomitization and dissolution. It also results in the heterogeneity vertically. So the lithology is the basic factor for the forming of internal reservoir of buried hill and the tectogenesis and diagenesis are key factors to improve it. The porosity in carbonate might experienced solution-cementation-resolution or recementation. The porosity evolution history was a kind of historical dynamic equilibrium. The internal reservoir of Ordovician carbonate is the comprehensive result of constructive and/or destructive diagenesis. The worm's eye maps of the early Paleozoic and middle-upper Proterozoic were plotted. It was inferred that the paleostress field evoluted from NNW to NW during the Mesozoic and Cenozoic. Three types of buried hills can be divided: C-P/Pzi, Mz/ Pzi and E/ Pzi. The unconformity of the buried hill of E/ Pzi type, comparatively, was formed and reconstructed latestly, t he p orous r eservoir c ould b e w ell p reseved. T his c ondition w as v ery favorable t o t he migration and accumulation of oil and gas and could form upstanding association of source-reservoir-cap rocks. The buried hills of Mz/ Pzi and C-P/Pz] type were took second place.

下扬子北缘前陆盆地形成演化与油气赋存条件

The foreland basin on the northern margin of the lower reach of the Yangtze river (the lower Yangtze foreland basin) is tectonically situated in the basin-mountain transitional area along the southeastern flank of the Dabie mountains. The early formation and development of the basin is closely related to the open-up of the Mian-Lue paleo-oceanic basin on the southern margin of the Central Orogenic System represented by Qinling-Dabei orogenic belt, while the tectonic evolution of the middle-late stage of the basin is mainly related to development of the Mian-Lue tectonic zone that occurred on the basis of the previous Mian-Lue paleo-suture. The foreland basin of the northern rim of the lower reach of the Yangtze river was formed during the middle-Triassic collision between the Yangtze and North China plates and experienced an evolution of occuirence-development-extinction characterized by marine facies to continental facies and continental margin to intracontinent in terms of tectonic setting.The foreland basin (T2-J2) was developed on the basis of the passive continental marginal basin on the south side of the Mian-Lue paleo-ocean and superimposed by late Jurassic-Tertiary fault basin. The tectonic setting underwent a multiple transformation of rifting-collisional clososing-tensional faulting and depression, which resulted in changes of the property for the basin and the final formation of the superposed compose basin in a fashion of 3-story-building. According to the tectonic position and evolution stages of plate collision happening on the southeastern margin of the Dabie mountains, and tectono-tratigraphic features shown by the foreland basin in its main formational period, the evolution of the foreland basin can be divided into four stages: 1) pre-orogenic passive margin (P2-Ti). As the Mian-Lue ocean commenced subduction in the late-Permian, the approaching of the Yangtze and North China plates to each other led to long-periodical and large-scale marine regression in early Triassic which was 22 Ma earlier than the global one and generated I-type mixed strata of the clastic rocks and carbonate, and I-type carbonate platform. These represent the passive stratigraphy formed before formation of the foreland basin. 2) Foreland basin on continental margin during main orogenic episode (T2.3). The stage includes the sub-stage of marine foreland basin (T2X remain basin), which formed I-type stratigrphy of carbonate tidal flat-lagoon, the sub-stage of marine-continental transition-molasse showing II-type stratigraphy of marine-continental facies lake - continental facies lake. 3) Intracontinental foreland basin during intracontinental orogeny (Ji-2)- It is characterized by continental facies coal-bearing molasses. 4) Tensional fault and depression during post-orogeny (J3-E). It formed tectono-stratigraphy post formation of the foreland basin, marking the end of the foreland evolution. Fold-thrust deformation of the lower Yangtze foreland basin mainly happened in late middle-Jurassic, forming ramp structures along the Yangtze river that display thrusting, with deformation strength weakening toward the river from both the Dabie mountains and the Jiangnan rise. This exhibits as three zones in a pattern of thick-skinned structure involved the basement of the orogenic belt to decollement thin-skinned structure of fold-thrust from north to south: thrust zone of foreland basin on northern rim of the lower reach of the Yangtze river, foreland basin zone and Jiannan compose uplift zone. Due to the superposed tensional deformation on the earlier compressional deformation, the structural geometric stratification has occurred vertically: the upper part exhibits late tensional deformation, the middle portion is characterized by ramp fault -fold deformation on the base of the Silurian decollement and weak deformation in the lower portion consisting of Silurian and Neo-Proterozoic separated by the two decollements. These portions constitutes a three-layered structural assemblage in a 3-D geometric model.From the succession of the lower reach of the Yangtze river and combined with characteristics of hydrocarbon-bearing rocks and oil-gas system, it can be seen that the succession of the continental facies foreland basin overlies the marine facies stratigraphy on the passive continental margin, which formed upper continental facies and lower marine facies hydrocarbon-bearing rock system and oil-gas forming system possessing the basic conditions for oil-gas occurrence. Among the conditions, the key for oil-gas accumulation is development and preservation of the marine hydrocarbon-bearing rocks underlying the foreland basin. The synthetic study that in the lower Yangtze foreland basin (including the Wangjiang-Qianshan basin), the generation-reservoir-cover association with the Permian marine facies hydrocarbon-bearing rocks as the critical portion can be a prospective oil-gas accumulation.Therefore, it should aim at the upper Paleozoic marine hydrocarbon-bearing rock system and oil-gas forming system in oil-gas evaluation and exploration. Also, fining excellent reservoir phase and well-preserved oil-gas accumulation units is extremely important for a breakthrough in oil-gas exploration.