The Relationship Between The Clastic Composition And The Pores Of Fuyu Oil Reservoir Sandstones In North Qijia Area

In sediment stratum , Quan four member , Songliao basin , are mostly volcanic material in fracture age of basin-edge . Relative with some other sedimentary basins , composition maturity and structure maturity of reservoir sandstones is lower . But reservoir properties is better , which is hand in glove with relatively developed secondary pore in volcanic material . This paper takes fuyu oil-reservoirs sandstone in north qijia area for subject investigated , Statistical analysis the Characteristics of the Clastic Constituents and how to influence reservoir properties . Generalize it to the study of reservoir sandstones formed by similar provenance .Secondary pore of this area is influenced by many facts , among them , clastic constituents is the most important one . Sedimentary source is a biggest effect on clastic constituents of reservoirs sandstone . By contrast to the lithological assemblages of some major provenances around sedimentary provinces and characteristics of light - heavy mineral groups of clastic constituents , this paper has judged the lithology feather of provenance and the tectonic settings of provenance by Dickinson triangular diagram .Depending on the proportion-increasing in heavy mineral of stable heavy mineral in clastic constituents away from provenance and the theory of sedimentary facies sequence arranging in turn according to sedimentary direction on plane coupled with the ubiety of deposite zone and provenance , as well as the developed situation of water system during the deposition , this text makes sure the deposite provenance of reservoirs sandstone . The lithology group of reservoirs sandstone in provenance is mid-acidic volcanic rock , the tectonic setting of provenance is the cutting-arc source region in volcanic arc , and the provenance is Daxinganling provenance in northwest basin .The lithology and locality of provenance controls the petrologic and mineralogical characteristics of reservoirs sandstone at a high degree .The slices were analyzed statistically by microscope . (1) the clastic constituents is mostly feldspar and bore meal , and their contents are comparative ; but the content of quartz is less and 28—40% ; the clastic constituents display the characteristic from mid-acidic volcanic rock provenance : Quartz is mostly single-crystal quartz whose surfaces have so small the fluid inclusionsfrom at a large and often solid phase inclusionsfrom of bigger particle and so little polycrystal quartz . The feldspars is mostly plagioclases , multiple twin is developed ; little k- feldspar ; clay mineralization is developed on the surface of feldspar . The bore meal is mostly volcanic rock bore meal , and so little sedimentary rock and metamorphic rock bore meal ; volcanic rock bore meal is mostly rhyolite,tuff,andesite and basalt bore meal .Terrigenous clastic heavy mineral have mostly zircon , white titanium mine,apatite,biotite,chlorite,epidote,magnetite , etc. . (2) The texture of reservoirs sandstone has close relation with the gathering of sandstone . The grain size of reservoirs sandstone is fine granular in the main , little middle granule ; the shape of rounding is mostly hypo-pointedness and little hypo-round ; the separation is moderate , most of grain size texture can be splited into two kinds : above 50% and 25-50% . (3) most of fillings are argillaceous , tuffaceous matrix and siliceous , carbonate cement . The physical stability and the pressure resistance of clastic constituents is relatively weak , the smaller grain size and the moderate separation lead to weak textural maturity ; the hole size among the original grains is less in burial fully grown rocks . By contrast , the stability of clastic constituents leads to the development of secondary pore and repairs in effect the narrow of primary pore and improves reservoirs sandstone properties of matter .The feldspar and the volcanic rock bore meal are of instable physical and chemical property , which becomes the prerequisite of the development of secondary pore .Conducting the stat of areal porosity by eleven wells and fifty-one casting body slices of the research zone .The areal porosity of secondary pore average out at 4% , the areal porosity of secondary pore middle granule is between 2—3%, more than 50% intragranular porosityare volcanic rock bore meal development , the content of volcanic rock bore meal in reservoirs sandstone is between 35—45% , the highest is up to 60% , which is leading clastic constituents ; therefore , the holes of granule of volcanic rock bore meal development are the important ingredient of secondary pore .By reference to the related data , the formation mechanism and formation process of volcanic rock lead to the instability of volcanic rock bore meal that is showed , from several aspects of component characteristic, texture structure and diagenesis , etc. , the reason of volcanic rock bore meal instability is discussed , the component is composed of vitreous , mafic mineral and feldspar , etc. , which are instable and changed easily ; Fluidal structure , vesicular structure , tuff texture and andesite texture of volcanic rock offer condition of secondary charge ; The rapid change of the temperature under crystal differentiation , condensation contraction and diagenesis forms the broken fissure of volcanic rock .By means of casting body slices , SEM , etc. , the vug , the casting-fenestra , the intercrystalline hole of granule , the contraction micropore and microfissure in the primary developed granule of volcanic rock bore meal are identified . Among volcanic rock bore meal secondary pore , the secondary pore under corrosion is the most important , other pores play a role of path and a important role in corrosion and make porosity become the effective one , although their ability of acting separately as reservoirs space is less , also , they offer a move path of corrosion solution and are enlarged by corrosion in themselves .To some extent , the development of volcanic rock bore meal intragranular porosity associates with depth , granularity , oil-invasion , etc. . The following rules are gained by the statistical analysis of depth , granularity , oil-invasion and the development of bore meal intragranular porosity : together with the accretion of depth , the areal porosity of intragranular porosity and the areal porosity proportion of intragranular porosity lift up , but the range is less ; they show weak positive correlation with depth . The areal porosity of middle-granule sandstone is higher than the one of thin- granule sandstone , intragranular porosity has better development than thin- granule sandstone , which show better advantage of middle-granule sandstone at aspects of the saving of pore and the development of secondary pore .The development of intragranular porosity in oil-invasion sandstone gets an advantage over non- oil-invasion sandstone .Just from the view of volcanic rock bore meal intragranular dissolved pore , the development of intragranular porosity is within clastic particles which is of the characteristic of small pore space and irregular geometric shapes , also , its reservoir ability and permeability are weaker ; and contribution to reservoir properties is less . But its corrosion reaches a certain degree and forms even casting-fenestra , also , porosity greatly improves . In addition , intragranular porosity combines with other pores in sandstone reservoir , which enhances permeability and improves reservoir properties . By casting body slice analysis , pore combinations are as follow a few kinds : The group of corrosion expanded intergranular pore , intragranular dissolved pore and casting-fenestra , the group of corrosion expanded intergranular pore , intragranular dissolved pore , casting-fenestra and tectonic fractures , the group of shrunken intragranular porosity , corrosion expanded intergranular pore and intragranular dissolved pore , the group of corrosion intergranular pore , corrosion intragranular porosity and carbonate cements internal bore , there in , the former two kinds have a bigger contribution to reservoir properties , but the second kind is uncommon , the first kind is the chief contribution in reservoirs sandstone .As for the traditional reservoirs sandstone , quartz is the chief clastic constituents , both compositional maturity and textural maturity are higher , primary intergranular pore develops , and it is the main reservoir space of oil and gas , the reservoirs sandstone formed at stage of rifting and subsidence is different to it , primary pore and secondary pore constitute the reservoir space , and secondary pore is over 30%.This paper mainly discusses the relationship between clastic constituents and primary , secondary pore , also , its effect on reservoir properties . I hope this paper could supply some help for the research of similar reservoirs .