Abstract:Well-pattern improvement and combined heterogeneous-phase flooding are initiated for the reservoir after polymer flooding and applied in Zhongyiqu Ng3 block, Gudao oil plant of Shengli oilfield. According to the reservoir conditions, the specific EOR project is designed, including 135 m×150 m well-pattern which can change the flooding direction and enlarge sweeping capability, and then fabricated the heterogeneous combination system combined with B-PPG, surfactant and polymer. The EOR project is applied, as the first candidate, on the Ng3 block and achieved great success. The injecting pressure and starting pressure rose 2.6 MPa and 2.7 MPa respectively, and resistant factor attained up to 2.2, showing that the flooding sweeping is more homogenous. The water cut of field pilot decreased by 14.5%, and the oil rate rose to 81.2 t/d from 4.5 t/d. The project has increased oil output by 43 000 t and recovery factor by 3.5%.

Abstract:The characteristics of offshore field (large well spacing, low well density) mean that the oil recovery is comparatively low during the operation period of platforms, normally 20 years. The surfactant-polymer (SP) flooding is a potential EOR method for offshore field. The key challenges of SP flooding offshore are: ①high salinity and high divalent cation concentration of the injection water; ②limited space on the oil platforms; ③severe sanding problem in the pilot reservoirs and serious interlayer contradiction. Regarding to the sand groups of Ng4-5 in Chengbei 1 block, Chengdao field, the thorough study on the key techniques of offshore SP flooding has been performed, including formulation design, injection allocation, sand control, and plan optimization. Our findings are described as follows: firstly, a fast dissolving and salt resistant SP system is developed so as to meet the offshore field development requirement; secondly, a series of small injection facilities are set up for automatic process, thus, the high-efficient integrated injection has been achieved; thirdly, the layered sand control and water injection technique with low shearing is established, and lastly, the reservoir engineering plan of SP flooding is optimized. Our study is significant for improving oil production rate and recovery factor in offshore fields.

Abstract:The heat-tolerance and salt-resistance hydrophobically associating water-soluble polymers is successfully synthesized by means of micellar copolymerization. The effects of initiator, solubilization surfactant, hydrophobic monomer and functional monomer content on tackify performance are studied. A preliminary evaluation is done on the heat-tolerance and salt-resistance performance,the long-term stability performance and oil displacement performance. With the increase of the concentration of calcium and magnesium ions in solution, the viscosity retention rates of HAWSP solutions are located in the range of 55%-60%, while the PAM’s rates only vary from 30% to 40%. After aging for 120 days at 90 ℃, the viscosity of HAWSP solution at the concentration of 1 500 mg/L is 15 mPa?s, while the PAM is precipitated after aging for more than 60 days. The experimental results show that the heat-tolerance and saltresistance copolymers have excellent viscous performance, long-term stability and good effect on oil displacement by using complex initiator Y4, surfactant NS, hydrophobic monomer molarity at 1.4-1.6 mol % and functional monomer AMPS-Na content of 15-17.5 wt%。

Abstract:The concentration of Preformed Particle Gel（PPG）could not be measured accurately by the regular test of polymer concentration. A new method of determining PPG content has been established, so as to ensure that plan optimization and field pilot test of heterogeneous combination flooding can be carried out successfully. The pretreatment condition of ultrasonic wave and centrifugal extraction are studied. Considering the property of nitrogen in PPG, the concentration of pretreatment PPG is measured by Chemiluminescent N-determining method. The results show that the optimal pretreatment conditions are obtained as follows: ultrasonic power of 500 W,ultrasonic time of 15 min, centrifugal rotational speed of 10 000 r/min, centrifugal time of 3 min and toluene as extractant. Under the conditions above and using the new method above, the relative error can be less than 4.0% of PPG concentration and the detection limit is 10 mg/L, fully meeting the requirement of the field application.

Abstract:There are some difficulties in the development of deep heavy oil reservoirs, including high oil viscosity, high percolation resistance, poor performance of conventional water flooding, high injection pressure and low injectivity. Based on the evaluation of surfactant adaptability, the influences of interfacial tension, permeability, injection rate and injection speed of surfactant slug flooding to improve water flooding performance for Dongxin oil field are investigated. The experimental results show that, the surfactants used have good compatibility with injection fluid, showing a better ability to reduce the oil-water interfacial tension. Under 70 ℃，the mass fraction of 0.01% surfactant solution and oil is lowered to 10-2 mN/m. After the injection of surfactant slug, the subsequent water flooding pressure is reduced evidently, the recovery efficiency is improved. Lower interfacial tension between oil and water, higher injection rate and lower injection speed can achieve higher injection pressure reduction and enhance the recovery factor by subsequent water flooding. The reduction of injection pressure can be up to 18%, and the recovery rate can be increased by 15.7%. In the same experiment conditions, for lower permeable cores, percolation requirements become tougher and the performance of surfactant slug flooding is poor.For the injection of 0.7 pore volume, the permeability falls from 256.65×10-3 μm2 to 36.16×10-3 μm2, and the subsequent injection pressure of water flooding falls from 17.1% to 10.0%, and recovery efficiency reduces from 15.7% to 11.7%.

Abstract:The key parameters and their values in the worldwide EOR technological limit for polymer flooding are compared in the paper. The main influence factors for polymer flooding are analyzed, and the distribution pattern of reservoir parameters in oilfields that have successfully applied polymer flooding is found. By considering the technical advancement and the application of polymer flooding,the new technological limits and parameter gradation series are established by using area percentage function of parameter distribution.The new technological limits for polymer flooding are used to evaluate the applicability of polymer flooding in 4 different reservoirs.The result shows that the new technological limits and parameter gradation series are applicable for the field research.

Abstract:The Shengli oilfield has rich remaining reserves after polymer flooding, the existing layer series and well pattern are not well prepared for its subsequent development. In order to further improve oil recovery and increase economic efficiency by subdividing layer series, this paper makes a study on layer adjustment for surfactant-polymer flooding reservoirs after polymer flooding in Gudong west 7 area, by means of numerical reservoir simulation. On the basis of chemical flooding of investment and cost analysis, a set of layer adjustment limit plates proposed to surfactant-polymer flooding reservoirs after polymer flooding has been established with the dynamic economic evaluation methods. Combined with the non-homogeneity composite index of each layer calculated by the entropy weight algorithm and the optimal partitioning scheme determined by the cluster analysis, we screen out the optimal partitioning scheme to meet the requirements. Taking this method to make layer adjustment for surfactant-polymer flooding reservoirs after polymer flooding, the results show that: after layer series adjustment, the recovery efficiency of Gudong west 7 area has increased by 3.45%, and the financial net present value has increased by 1.746 million yuan. The effect of layer adjustment is remarkable.

Abstract:Determination of incremental oil is the key to polymer flooding performance evaluation and economic analysis. For commonly used polymer flooding methods to evaluate incremental oil, the production decline analysis method is the most widely used, however,when production rate changes greatly during the process of polymer flooding, the calculation of incremental oil using this method will result in a great error. This method is improved in this paper for eliminating the impact of extracts. Also, the analysis is conducted compared with the numerical simulation method, which has confirmed the reliability of the method. Calculation examples for north Buzachi polymer flooding test wells group show that, the improved production decline analysis method can be comprehensive and objective for evaluation of the effect of increasing oil of polymer flooding, which will provide scientific guidance for decision-making on polymer flooding.

Abstract:During the flow of combined chemical flooding solution through porous media, the adsorption occurs for each component due to the long time contact with reservoir matrix. The optimized ratio of components may be changed and oil-displacing efficiency will be affected subsequently. The adsorption of each component in the unary, binary, and ternary formulations is evaluated. The interaction among the components of chemical flooding formulations is analyzed. The results show that, for the unary formulation, the maximum adsorptions of alkali and surfactant are 1.51 mg/g and 4.82 mg/g, respectively. For the petroleum sulfonate/polymer binary formulation,the adsorption of surfactant decreases to 3.55 mg/g. For the ASP formulation, the adsorption of alkali is increased to 1.70 mg/g and the adsorption of the surfactant and polymer keeps rising when the alkali concentration is higher than 1.0%. It can be seen from the interactions that, the polymer plays the dominant role which can reduce the diffusion rate when the alkali concentration is lower than 1%. Hydrolysis of the polymer plays the dominant role when the alkali concentration is higher than 1%.

Abstract:Molecular weight of polyacrylamide is one of the main factors affecting its properties. In order to increase molecular weight of polyacrylamide, an experiment study on the course of polymerization generation of polyacrylamide is conducted. Using refined acrylamide, sodium carbonate and water as main raw, by method of anterior alkaline cohydrolysis polymerization. This experiment analyzes the influence rule of initial reaction temperature, the dosage of chelator EDTA-2Na, hydrolysis time on the high Molecular weight of polyacrylamide, and confirms the synthetic conditions of high molecular weight of polyacrylamide. The results obtained provide the basis for the industrial production of polyacrylamide.

Abstract:With the development of reservoir performance, the reservoir fluid distribution in Baobei changes accordingly, and the permeability of reservoir gradually reduced as well. The currently injector spacing of Ⅰ-Ⅱ oil group is 260 m, it is difficult to establish an effective driving system, it is unable to meet the needs of current injection. The water injection intensity of reservoir is too high, and part of the injectors doesn’t work. This paper applies methods such as, section pressure gradient method, empirical formula technology of reasonable well spacing, investigation radius method, and economic limit well spacing method, and based on comprehensive comparative analysis of the advantages and disadvantages of various methods, and then proposes the reasonable spacing aboutⅠ-Ⅱ oil group in Baobei region. The analysis concludes that, the current injection well spacing of Ⅰ-Ⅱ oil group is too far. To establish an effective drive system and improve the oil displacement efficiency of producer-injector well, the reasonable well spacing should be 170 m (distance of the well spacing is related to oil prices). Under the existing conditions, the well spacing should be adjusted in field.

Abstract:Horizontal well multi-component thermal fluid stimulation high efficiency recovery technology is an EOR technology for heavy oil reservoir, which utilizes horizontal well, CO2, N2 and steam. The EOR mechanism is studied through horizontal well multicomponent thermal fluid stimulation experiment and numerical simulation based on the heavy oil reservoir characterization. Compared with the conventional steam stimulation, the horizontal well multi-component thermal fluid stimulation high efficiency recovery technology has three advantages: horizontal well can improve the injectivity and productivity and has a longer-term validity, the CO2 can significantly decrease heavy oil viscosity and residual oil saturation, in addition, the CO2 can also improve the displacement efficiency; the N2 can enlarge the sweeping volume and decrease the heat loss. The field application confirmed that this technology can significantly improve the steam utilization, decrease the injection pressure, improve oil well productivity, extend period of validity, and greatly improve the heavy oil reservoir of offshore reservoir.

Abstract:In order to forecast the productivity of perforated horizontal well, this paper introduced a three radial flow model based on the model used by Joshi in the derivation of horizontal well productivity formula. On the basis of the proposed model, this thesis derived out the productivity formula of perforated horizontal well with the equivalent flow resistance method, when the damaged zone is penetrated or not respectively. The productivity formulas takes many influencing factors into consideration such as the perforation length,shot density, perforation diameter, phasing, the diameter and the pollution degree of the damaged zone, the thickness and compaction damage degree of the crushed zone, the length of horizontal well, making the flowing mechanism more suitable for the real reservoir condition. The sensitivity analysis of the parameters with respect to the derived formulas shows: the productivity of perforated horizontal well rises with the increment of perforation length, shot density, perforation diameter, phasing, and the length of the horizontal well, and decreases as the thickness and compaction damage degree of the crushed zone increases. And, it is sensitive to the length of the horizontal well, perforation length, shot density and compaction damage degree, and is insensitive to phasing, perforation diameter, and thickness of the crushed zone. The perforation parameters is more sensitive with respect to the productivity index when the damaged zone is not penetrated than that penetrated. We should give priority to the length of the horizontal well, perforation length, shot density, and avoid excessive high compaction damage degree during the engineering design.

Abstract:The fractures of Dabei gas field are widely distributed in the multi-phase thrust-imbricate structure setting of Kuqa foreland. According to outcrop, drilling core, imaging well logging and experiment data, fracture characteristics, the distribution rule and their contribution to deliverability are analyzed herein. The fractures in study area are divided into two types, structural fractures and non-structural fractures, among which, the structural fractures account for 95%.The structural fractures are mainly composed of high dip-angle simple fractures and netted fractures, low dip-angle structural fractures are relatively rare. The predominant fracture orientation is near N-S which is in accordance with the current maximum principal stress axis, followed by near E-W trending fractures. In general, the fractures are characterized by high fracture density, minor fracture opening and high filling degree. With high porosity and permeability, the fractures of the second member of Cretaceous Bashijiqike formation are developed better than that in the third member in the vertical direction. Laterally, these fractures generally occurred in stress concentration area, such as outskirt of the anticline and near fault, while fractures in the core of anticline are relatively rare. The impact of fracture on single well productivity is mainly featured by its improvement on permeability which can access to 2 to 4 order of magnitude, among which, the fracture surface porosity and fracture density have the best correlation with productivity, fracture opening is a condition which is necessary but not sufficient to productivity. The study on fracture can provide reference for acid fracturing stimulation technology.

Abstract:The oil and gas exploration of Carboniferous has not made great progress for a long time in Qaidam basin. In this study,based on the research of sedimentary structure characteristics, hydrocarbon source rock geochemical characteristics, oil-source correlation of Carboniferous in Qaidam basin, we evaluate the exploration potential of oil and gas. The result shows that, the types of source rock are mainly consisted of mud shale, carbon mudstone, coal and carbonate. The source rock in the north of Qaidam basin has high abundance of organic matter, the organic matter is mainly of Ⅱ and Ⅲ types, ranging in mature and high mature stages, and has good potential of hydrocarbon generation. The multi-period tectonic movements control the forming period and later distribution range of oil and gas. The oil display situation in outcrop area and the result of oil-source correlation further confirm that, the source rock of Carboniferous has generated and expelled hydrocarbon, and the hydrocarbon accumulation obviously is controlled by tectonic action. The hydrocarbon generated in early phase, migration through fault, and adjusted reservoir accumulation are the accumulation pattern for Carboniferous reservoir, in the north of Qaidam basin.

Abstract:Structural transfer zone in northern Qiongdongnan basin is complex in structural features, the relationship between the structure and the hydrocarbon is not clear. Based on the seismic interpretation and geology research, the styles and development characteristics of structural transfer zone in northern Qiongdongnan basin are analyzed, and its significance for hydrocarbon geological is concluded with respect to reservoir, source rock, traps and migration. The research result shows that, there is convergent assemble and overlapping structural transfer zone, which can keep displacement and strain balance typically through branching secondary faults, turning faults strike and changing faults activity rate. Paleogeographic framework of the alternated source and depocenter in northern Qiongdongnan basin was developed at early rifting period, which controlled the development of high quality reservoir, hydrocarbon source rock, structural traps and hydrocarbon migration, and the paleogeographic framework made the structural transfer zone be of favorable conditions for hydrocarbon accumulation. The study shows that, the structural traps and structural-lithologic composite traps in this structural transfer zone are the favorable areas for hydrocarbon accumulation.

Abstract:Based on study of the component and its carbon isotope of natural gas samples from the J1b reservoir of Nanan-1 well, the J2-1 reservoir of Qi-34 well and the N1 reservoir of Du-87 well in the south margin of Junggar basin, we suggest that these natural gases are coal-related gas herein. But the natural gases sample data from the J1b reservoir of Nanan-1 well and the J2-1 reservoir of Qi-34 well are distributed at the region where natural gas originated from Type Ⅱ kerogen often locates in the Whiticar chart board. Natural gas carbon isotope and natural gas components show that, the secondary action should alter C1/C2+3 and δ13C1. In view of the geological background of south margin of Junggar basin, the genesis of unconventional natural gas from Nanan-1 well and Qi-34 well and Nanan 1 well is bacterial degradation, which resulted in C1/C2+3 increase and δ13C1 lightening, but the genesis of unconventional natural gas from Du-87 well is methane leakage effect. According to the distribution region of the unconventional natural gas, the different development direction of bacteria degradation gas and the coal-related gas leakage in methane component are pointed out. The research conclusion is a necessary supplement to the Whiticar chart board, and makes the Whiticar chart board more practical in the research work about natural gas.

Abstract:From the point of geochemistry, and combined with such geological elements as fracture distribution, sedimentary and tectonic conditions, according to accumulation systems classification principles, the Baiyun deep-water sag is divided into two broad classes，seven small classes of accumulation systems, that is, four accumulation systems in Panyu lower uplift in the western part and three ac?cumulation systems in Liuhua–Liwan district in the eastern part. We summarize the respective characteristics of different accumulation systems based on the following classification properties: sedimentary environment, crude oil classification, material source, oil source, crude oil maturity, oil and gas migration and accumulation, migration dominant factors. Three typical kinds of accumulation pat? terns are put forward on the basis of accumulation systems division, namely, open, closed and complex accumulation pattern. The open accumulation pattern has the features of multiple and developed faults, the faults play an important role in oil and gas migration and accumulation. The closed accumulation pattern is characterized by oil evolving into high maturity stage and cracking into gas thermally,fractures, ridge-like structures and sands are oil and gas migration channels. The complex accumulations are controlled by faults, diapir zones and ridge-like structures, high-degree evolution of petroleum cracking into gas thermally. According to the accumulation systems division in Baiyun deep-water sag, and the comprehensive analyses of three kinds of accumulation patterns, it indicates that, the N2, N3, N4 and E2, E3 are favorable migration and accumulation areas with good exploration prospects.

Abstract:Reservoir architecture is currently in the stage of development，and subsurface reservoir architecture is highly dependent on well logging data, so well deviation trajectory is of great significance to it. Based on calculation of well deviation trajectory, this paper proposes the formula of true thickness of reservoir architecture unit，taking the 4th（or 5th）reservoir architecture unit in Maill’s classification as study object. Studies have shown that well deviation trajectory would be misleading to identify all levels of reservoir architecture unit’s top or bottom surface and make the calculation results of reservoir architecture unit’s true thickness too large or too small in four different modes, including horizontal reservoir architecture unit, horizontal reservoir architecture unit when well deviation trajectory drill through fault, inclined reservoir architecture unit when its inclination is opposite with well deviation trajectory’s inclination, inclined reservoir architecture unit when its inclination is same with well deviation trajectory’s inclination; well deviation trajectory also brings about the wrong understanding of effective thickness and distribution of oil and water of the reservoir architecture unit. In order to grasp the reservoir architecture in different levels accurately, it is necessary to take into account of the impact of the well deviation trajectory step by step, from rough to detailed, and ultimately to provide effective guidance for later period of oilfield development.

Abstract:In order to recognize the exploration potential of Houzhen sag, the Houzhen sag are studied herein with respects to structure,paleogeographic environment and geochemical characteristics of the source rocks, hydrocarbon-generating conditions. Studies show that the Houzhen sag’s structure background is similar to Weibei sag that is adjacent to Houzhen sag. During the deposition of Kong 2 member, three sedimentary facies are developed: fan delta, shore-shallow lake, semi-deep lake. Most of the study area is controlled by the shore and shallow lake sedimentary face, and the fan delta face is developed on the north and south margins of the study area, the semi-deep lake face distributes until the east of Shouguang uplift, the south of Hou 2 well and adjacent to Weihe fault, and is favorable to development of source rock. The source rock of Kong 2 member of Houzhen sag is poor to medium source rock, and its thermal evolution is in stage of quantity hydrocarbon generation. Combining with drilling and seismic data, the thickness of source rock of Kong 2 member up to 100 m covers an area of 530 square kilometers. The Monte-Carlo method is used to calculate the hydrocarbon resource based on existing data, the hydrocarbon resource amount is 0.238×108 t at medium risk. A parameter well is proposed for accurate evaluation of hydrocarbon-generating conditions and reservoir forming conditions of Kong 2 member in Houzhen sag.

Abstract:The front sand of fluvial induced delta front is the most active deposition in the delta facies, and also one of the most important reservoirs in our terrestrial basin. The distributary channel and mouth bar in the delta front interact each other, and its evolution may be classified into three stages. The planar evolution may result in the vertical depositional differences, and according to the depositional difference, location and well logging curves, the vertical depositional in the delta front may be divided into 5 types: the single distributary channel, upper distributary bar, upper bar distributary channel, isolated bar and superimposed bar. Based on the guidance of modern delta study and depositional mode, the delta front sand in Sha II member of Yonganzhen oilfield is analyzed thoroughly to ascertain the combination relationship of distributary channel and mouth bar, as well as the planar distribution.

Abstract:Seismic inversion includes pre-stack inversion and post-stack inversion. There are some limitations when used alone, because both methods have different scope. It is hard to describe the reservoir in Yong3 area because of the complex geological condition.In order to solve this problem, the joint inversion is proposed based on a series analysis of rock physics, model, algorithm and interpretation. According to the advantage of each method in reservoir and fluid description, the unified model and algorithm are used to control the relevance, as well as improving the consistency and comparability of both results. The joint inversion of pre-stack and post-stack achieves a detailed description of the reservoir and fluid characteristics in Yong3 area with the prediction accuracy rate over 80% of Es2 layer.

Abstract:There develops compacted sandy-conglomerates with giant-thickness in the northern steep slope of Dongying sag, which are characterized by low permeability and porosity and complicated geophysical features, and the reservoirs are difficult to be identified.More than 100 core samples from 10 wells are selected, tested and analyzed by ultrasound. Based on the analysis of the experimental data and results, we determine the reservoir physical characteristics of sandy-conglomerates in the study area and conclude that the main factors which influence the seismic velocity of sandy conglomerates are porosity and lithology, the second is the cement content,and the variation is not obvious whether the micro-fracture exists or not. When different fluids are saturated in the rocks, P-wave velocity changes slightly while S-wave velocity doesn’t change. So, in the ideal state, we can identify fluid by the ratio of P-wave velocity and S-wave velocity.The relationship between the velocity and density of the rock is relatively good when the porosity is greater than 5% while poor when porosity less than 5%.

Abstract:Success rate and exploration benefit of turbidity prediction decreased in recent years, the main factor of which is the effects of carbonate. Starting with the characteristics of lithologic association, amplitude, vector and impedance, the carbonate geophysical response is studied deeply in Dongji sag of Dongying sag, and the recognition method of turbidity in carbonate background is proposed.The wavelet reconstruction, using wavelet decomposition by choosing the right wavelet, could remove the carbonate background and enhance the resolution. The ration of amplitude to frequency, which was calculated by attributes synthesis based on amplitude and frequency, is able to suppress the carbonate energy and strengthen the boundary information of turbidity. The ration of compressional wave velocity to shear wave velocity, which is calculated by pre-stack inversion technique, can also weaken the carbonate energy and beneficial to study the turbidity scale and the relationship with adjacent area.

Abstract:The tight reservoir with high closure stress in Junggar basin refers to the ones whose depth exceeds 3 500 m and closure stress gradient higher than 0.02 MPa/m, which is characterized by poor reservoir physical properties, high Young’s modulus and Poisson's ratio, and therefore leading to high fracture pressure. The typical reservoirs in Junggar basin mainly includes the Permian reservoirs in northwestern margin of Chepaizi uplift, Jurassic and the Cretaceous reservoirs and the ones penetrated by some risk exploration wells. There are many difficulties about the reservoirs: very high wellhead pressure, easy to form complex fractures because of natural fractures, proppant bridge because of the narrow fractures, high risk because of long time and high slurry rate, and so on. This paper presents 3 technologies: wellhead pump pressure reduction technology, proppant optimization technology and parameters optimization technology. These technologies can increase the well fracturing success rate of tight reservoirs from 50% to 100%. It has provided technical supports for the tight reservoir exploration and development of Junggar basin.

Abstract:Based on the characteristics of fluids suffering high shear stress caused by large pumping rate in slick water fracturing of shale gas reservoir, evaluation of four kinds of anionic drag reducer is carried out in laboratory at high shear rates utilizing large friction tester. The results show that, the drag reducer XT-65B has a better drag reduction efficiency, which can be up to 56%. Meanwhile, the factors affect the drag reduction efficiency, such as shear rates, shearing time and shearing path, are analyzed as well. With the increase of shear rate, resistance reduction rate of drag reducers is on the decline. At low shear rete conditions (500 s-1), the resistance reduction rate of drag reducers is not sensitive to the shear time; at the high shear rate conditions (5 000 s-1), the resistance reduction rate of drag reducers cut sharply with the increment of shearing time. Different shear paths affect the performance of drag reducers significantly,high shear rate can exert an unrecoverable damage on the molecular structure of drag reducer. The micro-structure of drag reducer molecule of XT-65B before and after shearing is also observed with the help of SEM, confirming that the drag reducer molecule is little affected at low shear rates（500 s-1）and degrades greatly at high shear rates（5 000 s-1）,which has a good agreement with the experimental results.

Abstract:The Yanchang oilfield has abundant low permeability reservoirs, and during the well completion process, the liquid invasion is the main factors accounting for the reservoir damage. In order to prevent the working liquid from damaging the reservoir, the perforating fluid for protecting reservoir is developed through modification of xanthan gum XG to get XG-HA as viscosifier by means of microwave method, so as to enhance the apparent viscosity by 80% and shearing up to 27 Pa under salt water of 4% weight. The formula of this perforating fluid is: clean water+0.8% to1.2%XG-HA+5%HFY+0.2%HEC+1% to 2%HCS-G+0.3% to 0.4% 4# surfactant+2% to 5%KCl. The solid free system passed the test, and the results show that the perforating fluid has low API filtration, and the viscous rheology is controlled in 8.2 mL, and cuttings recovery rate up to 91.23%, therefore, it is of high stain resistance and good demulsibility and biodegradation. The dynamic damaging and simulative experiments of core show that the core recovery rate with this perforating fluid system is 88.5%-95.3%. In Yanchang oilfield, the field application results show that, the system can effectively protect the reservoir and easy to be biodegraded, and therefore improving the single well production. This technique is feasible in field and worthy of being promoted.