Well JY1 is located in the east of Sichuan Basin.Commercial gas with high production has been tested and stable pressure and production has been maintained for long time by testing production in Longmaxi shale in well JYl.It marks the strategy breakthrough in marine shale gas exploration in complicated structural area at high thermal stage in southern China.According to the analyses of the structure,formation combination,lithology, TOC,RO,and mineral contents,combined with regional geological data,following conclusions have been obtained:(1)Structural and preservation conditions are the most important for shale gas to accumulate under the background of multiple structural evolutions and uplifts and erosions,which is different from that in North America;(2)Only the qualitative hydrocarbon rocks can play the role of detachment,and net-like fractures by multiple detachments and tectonic movements are key factors for shale gas abundance and high production;(3)The Upper Ordovician limestones take the role of sealing for the abundant shale gas in Longmaxi Formation;(4)Faults and uplifts made a few destructions to shale gas reservoirs.All implications above will have an exemplary meaning for shale gas exploration in southern China.
Because of the previous researches on occurrences of shale gas and the influencing factors of gas-bearing property being insufficient,combined with shale microstructure characteristics,pyrolysis simulation experiments on enrichment capacity of hydrocarbon gas have been systematically carried out with different types of shale at different mature stages,under different lithostatic pressure and fluid pressure and with different geological characteristics.It indicates that the extracted gas amount in shale,being relatively large,is closely related to their thermal maturity,namely the extracted gas productivity is very large at over-mature stage.The percentage of extracted gas with siliceous shale is the highest,calcareous shale is the second,while argillaceous shale is the lowest.For the same type of shale,the percentage of extracted gas is the highest at mature stage,which is intermediate at high-mature stage and the lowest at over-mature stage.Over pressure can obviously enhance the extracted gas productivity of shale.The bigger the over pressure coefficient,the higher the productivity of extracted gas.In the case of the same thermal maturity and evolution process of shale,the extracted gas production in the normal depth of shale is obviously higher than that in uplifted shale.The greater the burial depth,the higher the extracted gas yield of shale.Siliceous and calcareous shale possess high contents of brittle mineral,with big pore and fracture.Their porosity is relatively big,so the extracted gas capability is strong.While argillaceous shale has relatively low contents of brittle mineral,mainly developing micropore during hydrocarbon generation process and there is no big fracture,resulting relatively small porosity.Therefore,the extracted gas capability is weaker than that of siliceous and calcareous shale.The residual gas yields of shale are very low,and basically it does not have industrial exploitation potential,so the amount of field desorbed and lost gas is key in shale gas content determination.The gas-bearing property of shale is jointly controlled by organic matter content and the reservoir physical property.Overpressure is the key of high production of shale gas,and shale gas enrich in dark and dark grey shale with calcareous (lime),siliceous and sandy thin layer (interlayer),developing better foliation.
The coal resource is abundant in Zhijin-Nayong Coal Field,Guizhou Province.The coal resource is up to 2.22×1010t.CBM resource in the Zhijin-Nayong region is up to 1.6×1012m3,which is because that coal measure with high metamorphic degree is favourable for CBM formation.In this paper,on the basis of the characteristics of coal measure,and the content and component of some main coal measures(M13,M15,M21,M29,M32,M34),CBM resource of Niuchang syncline,Zhijin,Guizhou was studied in detail.The result shows that CBM resource in the coalfield is up to 18.39×108m3,and that CBM resource in central syncline is more than that in the wing of syncline.
By considering the effect of the deformation of coal or rock in reservoir,skeleton coal powder stripping,coal powder migration and deposition in pore,and coal powder block at pore throats on the physical property parameters of coal or rock (such as porosity,permeability,pore compressibility and density et al),and considering the solution of coalbed methane in water and fluid source sink term,a mathematical model of fluid-solid coupling percolation with coal powder in coal reservoir is established,which provides theoretical foundation for numerical simulation of CBM development.
Kuqa Depression of Tarim Basin is located in piedmont of the southern Tianshan Mountains.Extensive thrust structures developed in the depression because of the intense extrusion in Late Cenozoic.Also,under the combined effects of thrust salt rocks deformation and rock salt deformation,the interior of Kuqa Depression formed a series of complex tectonic styles,among which,special ceiling structure formed in squeezing deforming process of structural bed on the salt bed.And the ceiling structure had great influence on the tectonic deformation of both the salt bed and underlying bed.This kind of deformation structure was studied in this paper through comprehensive seismic and drilling data.The results showed that:(1)The ceiling structures were common in the structural layer above the salt bed in the foreland thrust belt of Kuqa Depression,and correspond to two rows of linear folded belts in Kelasu and Qiulitager tectonic belts on the earth surface.(2)The ceiling structure could be classified into faulted type and folded type on the basis of structural elements,and the former could be subdivided into symmetrical faulted type,one-way faulted type and overlap faulted type,while the latter could be subdivided into arched type and spherical type.(3)The ceiling structure had ceiling effects,including stress adjustment,decompression effect and seal-capping,which had influenced the tectonic deformation,reservoir evolution and petroleum entrapment of the structure under the salt layer.Also,the ceiling structure was good for the accumulation of oil and gas in the foreland thrust belt of Kuqa Depression.
According to the results of experimental methods such as polarizing microscope,scan electron microscope and cathode luminescent,and previous published research results,the characteristics of diagenesis and diagenetic facies of reservoir in He8 section of Shihezi Formation in east Ⅱ part of Sulige Gas Field were studied.Meanwhile,the test results of fluid inclusions were also considered.The diagenetic evolution was divided into four stages including six phases.In the process of diagenetic evolution,the dissolution in late period B of early diagenetic stage to early period B of middle diagenetic stage is so important that produces lots of secondary pores,and because of the dissolution,this stage is the key time to form constructive diagenetic facies.According to the study of petrology and diagenesis,there were five diagenetic facies types,and the logging characteristics of each diagenetic facies were set up.After analyzing the diagenetic facies of single well,diagenetic facies in vertical are characterized by dissolution facies in the below and compaction facies in the upper,and the plane distribution is confined by sedimentary facies.The dissolution facies of unstable components of sandstone with low pore and permeability are the most constructive facies which distribute isolatedly.
Based on core observation and detailed lithofacies analyses in the Cenozoic section,using plenty of analytical data of grain size,a large number of probability cumulative grain size curves in the main terrigenous depositional environments of the northern Qaidam Basin were summarized.The results show that the study area mainly developed alluvial fan deposit in the Lulehe Formaition（E1+2）,braided river in the Lower Xiaganchaigou Formation（E13）and braided delta in the Upper Xiaganchaigou Formation（E23）.Each sedimentary facies is divided into several subfacies and microfacies again.The characteristic of probability cumulative grain size curves in different sedimentary facies are as follows:The probability cumulative grain size curves of alluvial fan include typical “bi-segment” pattern,i.e.,“one suspension” and “uphill arched arc” pattern;The braided river facies have “bi-segment”,“high slope one bouncing population-one suspension population-transitional zone” pattern and “tri-segment” pattern;The braided delta facies contain typical “bi-segment”,“tri-segment”,“one bouncing population-1suspension population-transitional zone”,“high slope one bouncing population-1suspension population-transitional zone”,“low slope multi-bouncing population-one suspension population”.Each sedimentary subfacies has its own peculiar probability cumulative grain size curves.
The altitude in Qaidam Basin has getting higher since Cenozoic because the basin has been in the structure setting of the Tibetan Plateau continuous and periodical uplifting,which makes the basin have a close,dry and cold environment and abundant salt source.This typical plateau saline lacustrine basin generally precipitates salts in relatively deep water.The source rocks developed with the salts in the zones,which usually have hydrodynamic break,such as footwall of large syndepositional fault,due to the double-diffusive convection.Although the TOC of source rocks in this type basin is widely low,excellent kerogen types,high hydrocarbon conversion rate and good preservation conditions still can make them as high-quality source rocks.Plateau saline lake has a favorable environment to develop sandbodies of underwater distributary channel,estuary bar and beach bar,which usually distribute below the slope break belts.It is easy for it to develop lithologic traps because the reclusive fluid system and strong cementation.So the key point of hydrocarbon accumulation is the carrying capacity of fracture-sand conducting system.It is obvious that slope break belts controlling the sandbodies and hydrocarbon accumulation along the fractures in plateau saline lake basin.In summary,the favorable areas for lithologic reservoir are below the slope break belts with rich conducting fractures.
According to the comprehensive research of source rock burial history,geothermal history,organic matter maturity history,hydrocarbon generation rate evolution and cumulative hydrocarbon generation amount in the Dongling slope belt of Changling fault depression,it is considered that the source rock of K1h1 had two massive hydrocarbon generation and expulsion effects,which happened at the sedimentary end of K1hand during the basin depression stage.The first hydrocarbon generation and expulsion stage resulted in many self-generated and self-stored lithologic and stratigraphic oil reservoirs of K1h,while the second hydrocarbon generation and expulsion stage resulted in many structural and structural-lithological oil and gas reservoirs of K1h and its overlying fault-depression formations.The hydrocarbon accumulation process of the two expulsion stages can by concluded to the subtle oil reservoirs accumulation model of the fault-depression period and the structural oil and gas reservoirs accumulation model of the depression period,the next exploration direction can thus be pointed out according to the accumulation models.
Beijiao Sag lies in the deepwater of Qiongdongnan Basin.It is surrounded by some uplifts and deserves researching in order to find a new exploration area.Using comparative analysis method,by dissecting Yacheng Formation in Yabei Sag carefully,we can know sedimentation and source rock characteristics of Yacheng Formation in Beijiao Sag.Combined with drilling wells′ geochemical index,geothermal characteristics,reservoir-caprock assemblage,we evaluated the exploration potential of Beijiao Sag and obtained the following conclusions.During rifting stage,Beijiao Sag was a half graben.The sub-sag of Yacheng Formation has an area of 1 400km2 and maximum thickness of 2 150m.Compared to the Yacheng Formation of the Yabei Sag,it has similar ancient landform,seismic reflection and sedimentation characteristics.The deposition environment belongs to marine-terrestrial transitional lagoon-tidal flat facies.Coal measure from tidal flat is the dominant source rock,and the lagoon mudstone is important source rock as well.Drilling wells have proved Beijiao Sag can form highly mature coal-derived gas and there are many sets of reservoir-caprock assemblages around the sag.This sag has good exploration potential.
Based on the analysis of general thin-section,casting lamella,scanning electron microscope,X-ray diffraction and other analytical methods,the characteristics and evolution of diagenetic porosity of Huagang Formation of Paleogene in the central anticlinal belt of Xihu Sag were studied in detail.The result shows that feldspathic-lithic quartz sandstone is the main sandstone type,with medium maturity of texture and component.Diagenesis is the main controlling factor of reservoir physical properties.During the process of diagenesis,compaction and cementation are the main destructive digenesis,while dissolution is the constructive digenesis.Vitrinite reflectance and other data indicate that Huagang Formation in the northern part buried deeper than 3 600m is at B-period of middle diagenetic stage,while that of the southern part is at A-period,which shows that the reservoir condition of southern part is better than that of the northern part.
As major substitution to supply oil and gas resources for human needs,deepwater (also known as deepsea) has become strategic places for many countries.Compared to land and shallow waters,science and technology play an important role in the exploration and development of deepwater oil and gas.By systemic research and detailed analysis of geological characteristics,exploration technology (seismic technology and non-seismic technology) and mining technology (risers technology,development wells' drilling technology,completion and recovery technology) of deepwater oil and gas,future trends of the science and technology of deepwater oil and gas were summarized in combination with the development plans of major international oil companies.Also shown are the themes of the famous international conferences about oil and gas held in recent years and test results obtained by oilfield service companies.At the same time,a few suggestions for China's future development in the field were proposed.
Lower Jurassic Zhenzhuchong Formation and the second number of Upper Triassic Xujiahe Formation are two main gas production strata of Jiulongshan Gas Field,however,no conclusion has yet to be reached about gas source for the both strata.Therefore,this contribution makes a detailed analysis about the gas component,carbon isotopic composition,source rocks and reservoir bitumen biomarkers,to clear the gas sources of Zhenzhuchong Formation and the second number of Xujiahe Formation.There are 2 offsets of high quality hydrocarbon sources:the shales of shallow Xujiahe Formation (third number),limestone of deep Maokou Formation and mudstone of Lower Cambrian.In general,gas is dry,and gases from both the Zhenzhuchong Formation and the third number of Xujiahe Formation have similar characteristics,while gases from the second number of Xujiahe Formation have combined characteristics of both shallow and deep gases.δ13C2value is averaged at -26.73‰ for the gas from Zhenzhuchong Formation，which is similar to the Xujiahe Formation coal source of periphery Wenxingchang and Zhongba Gas Fields.Theδ13C2 value is from -29.5‰ to -30.49‰ for the gas from the second number of Xujiahe Formation,which demonstrates characteristics of both shallow coal-derived and deep oil-derived gas.Zhenzhuchong Formation has high tricyclic terpane value and rearrangement sterane/steranes value,which is the same as Xujiahe Formation.C27/C29value is from 0.93 to 1.00，like shape “V”.The second number of Xujiahe Formation has similar low tricyclic terpane values and rearrangement sterane/steranes to that in Maokou Formation.Therefore,it is concluded that gases in the Zhenzhuchong Formation is sourced from the third number of Xujiahe Formation,while gases in the second number of Xujiahe Formation are mainly derived from both the third number of Xujiahe Formation and deep Maokou Formation.
Pyrolysis-GC thermal simulation experiment has been performed on the light hydrocarbon generated from the marine source rocks of central Tarim Basin,China and the monomer hydrocarbon isotope.It is concluded that the main generation stage of light hydrocarbon occurred when the RO ranges from 1.3% to 1.9%.The branch alkanes are the principal components among all the compounds with the abundance of naphthenes and aromatics being relatively close.Relatively lower carbon isotopic values have been observed in benzene and toluene which are lower than -25‰ in general.Carbon isotopic values of cyclohexane and methylcyclohexane are generally lower than -24.1‰,which are also quite low.According to the analysis of the composition and carbon isotope of the light hydrocarbon of the oil-associated gas in Tarim Basin,it is concluded that it is mainly composed of the branch alkanes which accounts for from 45.4% to 93.7% with an average of 70.1%.The proportion of naphthenes is from 5.4% to 40.6% with an average of 23.4%,with that of aromatics being at a low level.The carbon isotopic values of benzene and toluene range from -23.7‰ to -28.6‰ and from -23.7‰ to -29.5‰,respectively.The carbon isotopic values of cyclohexane and methylcyclohexane are lower than -26‰,which are obviously lower than those from the foreland basin in Tarim Basin.In addition,gas-source correlation of the gases in central Tarim Basin has been discussed in this paper based on the carbon isotopic analysis.
The geochemical characteristics of natural gas play an important part in the research of accumulation mechanism.The characteristics of gas component and its carbon isotope in Kelasu tectonic zone were discussed,and the maturity of the natural gas was analyzed.It is indicated that natural gas in this large gas field is dominated by hydrocarbon,and the content of methane accounts for more than 90%.The dryness coefficient is over 97%,which indicates the natural gas is dry gas.The value of δ13C1 is from -33.1‰ to -25.1‰,and the main distribution interval is from -32‰ to -28‰.The value of δ13C2 is from -28.1‰ to -16.81‰,and the main distribution interval is -20‰ to -18‰.In general,natural gas in the overpressured large gas field from Kelasu tectonic zone is typical dry gas with high carbon isotope of methane and ethane.Our research result has important designative meaning for accumulation of overpressure large gas field.
The low permeability oil and gas resources include tight sandstone gas reservoirs and low permeability reservoirs,which have an important practical significance to increase the reserve and production in the current oil and gas exploration.Oil and gas geochemical exploration has the same exploration concept with the current dynamic oil and gas resource exploration,and has an advantage in low permeability oil and gas resources exploration.It is effective that geochemical anomaly indicates the reservoirs spatial distribution above the Yingnan 2 well in tight sandstone gas reservoir.Geochemical indicators causing high content of anomalies demonstrate the poor preservation condition of gas reservoir and the heavy lost of accumulated gas.The anomalous distribution characteristics of the geochemical indicators such as SC1 and SC+2,DC1 can effectively reflect the distribution of the low permeability oil and gas area of an Ordos Oil Field.It plays an important role for geochemical exploration technology in the low permeability oil and gas resources exploration based on the two regional geochemical explorations.
The behaviors of absorption and desorption of light hydrocarbons in marine sediments were studied in laboratory by injecting light hydrocarbon mixed standard gas into the degassing marine sediments.The results of absorption show that the changes of light hydrocarbons are caused by solution and absorption primarily.The smaller the carbon numbers of light hydrocarbon molecules,the easier the solution.The bigger the carbon numbers of light hydrocarbon molecules,the easier the absorption.Meanwhile,the olefins are more prone to solution than the alkanes of the same number of carbon atoms,and the n-alkane are more prone to absorption than the i-alkane of the same number of carbon atoms.The results of desorption tests show that thermal desorption can play the role of desorption,and dissolved light hydrocarbons are more prone to desorption than absorbed ones.
The Xujiahe Formation in Baimiao area in the middle part of Sichuan Basin has frequent oil and gas shows in drilling and it indicates tremendous exploration potential.It is important to develop the study of oil-gas detection in the Second Member and the Forth Member of Xujiahe Formation.The detection of distribution of favorable oil and gas range in the target strata is based on the fluvial detection principle and flow in two-phase medium,i.e.,based on the phenomenon of “low frequency resonance and high frequency attenuation” of seismic response of underground two-phase medium.The wiggles of seismic data are intact and complete.There are no phenomena of cut value and cutoff frequency,and the quality of seismic data is good.The seismic response of reservoirs of the Second Member and the Forth Member of Xujiahe Formation represents weak amplitude,good continuity and low frequency.According to the fluvial detection flow in two-phase medium,the oil-gas detection has been realized on 29 two-dimentional seismic profiles in the total thickness of 890km of the Second Member and the Forth Member of Xujiahe Formation in the study area.Implementing the oil-gas detecting result of two-target strata of the two members on every seismic profile,final plane figures are separately completed,so that the favorable exploration area is determined,which is of actual significance in expanding the exploration realm and in searching for new exploration areas.
Considering the difficulty of identifying fluid contacts on seismic profiles which have no significant fluid responses,the method and application prerequisites of Common Contour Binning Stacking Technique for Pinpointing Gas-Water,Gas-Oil and Oil-Water Contacts,which is able to tackle the problem mentioned above,was introduced.Common Contour Binning Stacking Method is based on 3D seismic waveform stacking and enhances the amplitude variances resulted from fluid type change in order to identify the fluid contacts which have no significant seismic responses.Through this method,the fluid contacts of anticline gas reservoir which has “flat spot” and structural-lithological trap reservoir that has no “flat spot” have been identified.The application results and effectiveness of Common Contour Binning Stacking Method have been discussed and the application prerequisites have also been summarized.
Dagang Oilfield shallow gas reservoir is referred to those with burial depth lower than 400-1500m.Problems exist such as small scale,insufficient gas reservoir energy,and difficult to to be detected.Seismic hydrocarbon detection technology can solve the above problems and achieved good results.Using the pre-stack detection technology which is based on elastic medium model,adopting AVO method to build the forward model,the 3-D seismic data from Dagang District are processed.Gas-bearing prediction has been done according to the AVO anomaliesand it demonstrates the distribution of sandstone with good gas-bearing propert.With the energy absorption analysis technology which is based on the viscoelastic medium model.Shallow gas detection and lateral prediction of very shallow strata have been carried out.The gas highlight characteristics are remarkable.Two potential gas-bearing areas are predicted.With the prediction of seismic attribute gas layer,it is found that the average energy attribute is sensitive to the reaction of gas layer in the study area,and thus determined the plannar distribution of gas reservoirs in the study area.Via the application of the earthquake information reservoir gas-bearing prediction technology,it is expected that there will be 5-6 billion cubic meters of newly added shallow gas reserves.10 target blocks have been screened out and used as a preferred target for future production capacity construction.
On the basis of the comprehensive explanation of seismic,logging,and geological original materials,the Es42 of 28 block of Shengtuo Oilfield was taken as the research object.The Petrel reservoir modeling software was used to establish the structure and sedimentary microfacies models.Moreover,under the restriction of sedimentary microfacies,stochastic simulation was applied to predict reservoir parameter between wells,and the reservoir property model was finally established.By comparing the phased and non- phased models,it is found that phased modeling technology could realize the correspondence between reservoir property and distribution of sedimentary microfacies.The results could also factually reflect the vertical and lateral heterogeneous and connectivity of reservoirs.Verified by the real reservoir geological understanding,it confirmed the rationality and scientific nature of the phased modeling,which can provide guidance to the development design in future.
There is no clear answer for how the development of gas reservoir has been influenced by the stress sensitivity of rock.The rock stress mathematical model and physical simulation experiment have been established to study the characteristics of stress changing during well drilling and the influence of the stress sensitivity on gas reservoir development.On the basis of the rock stress mathematical model,the changing rule of rock stress along with “time and space” has been analyzed.Many cores from different gas fields such as Sulige and Xujiahe have been tested under different stress conditions.In the physical simulation experiments,the influence of stress sensitivity on some development index such as the stabilized production of well,the gas producing velocity of reservoir and the gas reservoir recovery have been researched.Some new understandings have been drawn which are significant for scientific development of gas reservoir.
Based on indoor waterflooding results of 28 core samples from two super-low permeability reservoirs with different lithology of sandy gravels,fine siltstone and the results of conventional displacement experiment,and contrast test and immersion test using casting thin sections,the improvement of displacing phase permeability and displacement efficiency brought by modified injectant OR and DA in different rock samples was evaluated,the mechanism of percolation ability enhancement brought by modified injectant was analyzed,then the optimization of injection concentration of modified injectant was conducted and the better one went into field test.The study shows that OR is better suited with fine siltstone super-low permeability reservoirs,while DA is better suited with sandy gravels super-low permeability reservoirs.Both of them can improve the displacing phase permeability and displacement efficiency,while reduce oil-water interfacial tension to some extent.The immersion test shows that both modified injectants can corrode the interstitial material filling the rock pores,and the reasonable injection concentration of modified injectant OR and DA are 3 000mg/L and 2 000mg/L respectively.While the field test shows that modified injectants can actually reduce water injection pressure by 2.76MPa on average,increase the daily water-injection rate by 4m3 and the water-injection situation is also improved.Both indoor experiments and field tests show good results.
Recently,for horizontal wells in tight sandstone reservoir with low permeability,there is still no reasonable and effective log interpretation method for accurate evaluation of hydrocarbon potential of such reservoir.Through directly admitting the physical sample back to the wellbore,the mud logging technique can visually and effectively collect and evaluate the hydrocarbon-bearing information.The results of the evaluation is relatively more convincing.In comparative study for multi-horizontal wells of Honghe Oil Field,the data of well logging interpretation,comprehensive mud logging evaluation and production test did not show much consistent positive correlation,and even have great difference in a portion of wells.In view of such differences,the author compared and analyzed data in detail between the mud logging and e-logging of many horizontal wells in the study area,discussed among the feature and principle of each measurement parameter,summarized the main controlling factors which caused explanation differences,put forward the complementary advantages of both parties through the measured parameters,finally establish a set of comprehensive evaluation method,which maximize the role of all the quantitative and qualitative parameters.Thus it provides an effective way for accurately evaluating the hydrocarbon potential of such reservoir.
The exploitation of gas condensate reservoir needs accurate phase behavior data,especially the dew point pressures of gas condensate reservoir fluid.By considering the characteristics of gas condensate reservoirs and analyzing the merits and demerits of the existing correlations in literatures for dew point pressures,a new empirical model for predicting the dew point pressures of gas condensate reservoirs was developed,which involving the parameters of the reservoir temperature,gas composition,and C7 plus component properties.Fourteen groups of gas condensate samples from different areas in China were selected to examine the applicability of this new correlation by comparing with several other correlations and thermodynamic models.The results show that the total average absolute deviation of this new developed model is only 1.24%,much better than those calculated by other methods in literatures.The new model also has a wide application range,with methane composition of 65.59%~93.09% and gas-oil ratio for gas condensate reservoir of 1 002~63 377m3/m3.
Compared to common vertical wells,horizontal wells have great advantage in improving individual well producing rate,rapidly establishing productivity and excavating the potential of the old producing area.The rapid development of geologic steering technique of horizontal well make it possible to greatly improve the reservoir drilling rate and overall develop oil and gas fields.In view of the tight sandstone gas reservoirs which have characteristics of fast transformation of fluvial facies,overlapped sandbody,this paper applies advanced geological tracking software,combining the 3D geological modeling and traditional geological tracking technology,and makes fully use of LWD real-time data,from the design,landing into the target to horizontal drilling,and puts forward the relatively perfect thought of geologic steering:carve model,real-time contrast,grasp the landing point;update model,correction of understanding,timely adjustment.And then,it takes the real drilling of HW well for example.With this technique,it obtained average sandstone drilling of 90% and effective reservoir drilling rate of 64%,and makes great production effects combined with the late hydraulic fracturing,which has high reference and application value to the same type of gas reservoir exploration and exploitation.
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