Table of Content

01 December 2016, Volume 38 Issue 6

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Research on Mechanical Driven Crown-Block Heave Compensation Device

LIU Qingyou, XU Tao, HAN Yiwei

2016, 38(6):  1-7.  DOI: 10.11885/j.issn.1674-5086.2015.03.04.14

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Hydraulic driven crown-block heave compensation device is widely used due to the mature technology on floating drilling platform in the process of deep-water operation. However, the hydraulic driven system is characteristic of delayed reaction and low compensation accuracy. This paper proposes a mechanical driven crown-block heave compensation device which has a driving gear-driven gear-straight rack rail as the compensation driving force transmission mechanism and a driving motor as the power source of compensation, to improve the accuracy and efficiency of the crown-block heave compensation device. Based on the analysis of the working principle of the device we put forward the concrete structure of mechanical driven compensation device, carried out stress analysis of the driving gear and driven gear in the process of transmission, and get the load distribution of two gears in the process of heave compensation movement. By adopting the dynamic method, we analyze the driven gear and straight rack rail in the transmission process, and establish the dynamic vibration analysis model of the gear and rack in the meshing process and get the torque balance equation, and we find out that the mechanical driven structure produces certain vibration excitation to the straight rack rail.

Source Supply System and Reservoir Forming Model Prediction of Natural Gas Hydrate in the Deep Water Area of the Northern South China Sea

HE Jiaxiong, LU Zhenquan, SU Pibo, ZHANG Wei, FENG Junxi

2016, 38(6):  8-24.  DOI: 10.11885/j.issn.1674-5086.2016.09.03.01

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Although differences exist in formation conditions between natural gas hydrate reservoirs and petroleum accumulation, they also have some requirements in common. Both of them need the spatiotemporal coupling configuration between sufficient hydrocarbon source supply, source supply transportation system and favorable gathering places. In order to further study the differences in formation conditions, this paper deeply analyzes the gas sources composition of petroleum and gas hydrate, and the characteristics of fluid migration transporting system, based on the tectonic sedimentary evolution, petroleum geological conditions, and oil, gas and gas hydrate exploration results of the northern South China Sea continental slope areas in the past. In addition, according to the analysis results of geology, geophysics and geochemistry, the space-time coupling configuration relationship between the types of gas migration channel system and the gas hydrate stability zone characterized by high pressure and low temperature are also dissected synthetically. Based on the basic geological conditions of oil/gas and gas hydrate reservoir, three models of natural gas hydrate formation and accumulation in northern slope deep-water area of South China Sea are summarized and established, "biogenic gas accumulated in place by way of self-generation and self-bearing", "thermal gas accumulated offsite through faults and fractures by way of lower-generation and upper storage", and "thermal gas accumulated offsite through mud diapir and gas chimney by way of lower-generation and upper storage". This paper hopes to provide decision-making basis and guidance for the prediction of natural gas hydrate resources and the favorable exploration target evaluation in the deep water area of the northern South China Sea.

The Impact of the Interlayer of No. 16 Pebbled Sandstone Member in Tarim on the Distribution of Oil and Water

YIN Nanxin, LI Cungui, LI Zhongchao, XIONG Yunbin, LUO Yanan

2016, 38(6):  25-34.  DOI: 10.11885/j.issn.1674-5086.2015.02.02.03

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As the distribution of barriers and baffles could seriously affect the result of water flooding development, the paper took No. 16 pebbled sandstone member of Donghe reservoir at Middle Tarim as study area. We divided barriers and baffles into different types according to genesis mechanism, analyzed the characteristics of well logging response of different types of barriers and baffles from data of typical wells and predicted the spatial distribution of barriers and baffles and discussed the relationship between barriers and baffles and the distribution of remaining oil. The research shows that muddy interlayer, calcareous interlayer and low-permeability shaly sandstone interlayer are the main types of interlayer in of the study area; calcareous interlayer is at the bottom of the 5^th sublayer, muddy interlayer concentrates at the bottom of the 3^rd sublayer and low-permeability shaly sandstone interlayer is found sparsely. The vertical permeability of fluid is affected by the interlayers, which results in two oil-water pressure systems. In the same pressure system high-permeability reservoir is water-washing zone and low-permeability reservoir is remaining-oil rich zone. The study on the causes, type and distribution of interlayers, made clear the characteristic of enrichment of remaining oil and distribution of oil and water and provided geological evidence for the development program adjustment of next stage.

Methods of Cutoff Determination and Applicability Analysis in Low Porosity and Low Permeability Reservoir

CUI Yufeng, WANG Guiwen, SUN Yanhui, WANG Di, LI Ruijie

2016, 38(6):  35-48.  DOI: 10.11885/j.issn.1674-5086.2015.02.04.05

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Low porosity and low permeability oil and gas reservoir is of huge potential. Cutoff plays a very important role in the process of reservoir evaluation. The domestic and overseas scholars have done a lot of researches, but there still lack method comparison and applicability research. Therefore, after literature review, this paper elaborates the origin and definition of cutoff, and summarizes the influencing factors with examples. On that basis, we summarize three kinds of methods of cutoff determination:methods based on core data, methods based on core and test data, and methods based on logging data. The applicability of each method is illustrated. We suggestthat the methods be selected according to geological backgrounds and data available, and cutoff determination results be tested and supported with different methods. Based on the above research, we analyze the development trends of researches on cutoff pay hoping to lay a foundation for further researches.

Geological Characteristics of Wufeng-Longmaxi Formations in Southern Chongqing-Northern Guizhou Area

KANG Jianwei, YU Qian, YAN Jianfei, SUN Yuanyuan, QI Minghui

2016, 38(6):  49-60.  DOI: 10.11885/j.issn.1674-5086.2016.06.07.01

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Through observation of outcrop, drilling core and the organic-rich mudstone in Wufeng-Longmaxi, and with organic geochemistry, microscopic section, X-ray diffraction, pore permeability, specific surface area, and scanning electron microscope, we analyzed the basic geological characteristics of shale gas reservoir in Wufeng-Longmaxi formation. The analysis shows that the Wufeng-Longmaxi shelf environment is the foun-dation of organic rich mud shale. The sedimentary pattern of shallow shelf and deep water shelf determines the mudstone distribution which is thin in the South(10-80 m). Deepwater mudstone average organic carbon content is greater than 2.0%, and the organic matter is of type I kerogen of sapropel type, with high degree of maturity(R_o=0:82%-3.04%). The reservoir is of low porosity and low permeability, with various micro pore structures.Through shale gas block assessment and selection, we conclude that the Anchang-Daozhensyncline area is of favorable geological conditions for shale gas enrichment and has a good prospect for shale gas exploration.

A Study on Fine Sedimentary Sequence of Shale in the Continental Rift Basin of Jiyang Depression

WANG Yong

2016, 38(6):  61-69.  DOI: 10.11885/j.issn.1674-5086.2015.06.23.04

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Integrating the geochemical elements, sedimentary environment restoration indicators, lithology and gamma spectroscopy logging response, we studied the fine shale sedimentary sequence on the Es₄s-Es₃x of Jiyang Depression, and the results show that, during the formation process of fine-grained sedimentary sequence, the sequence boundary, affected by depositional environment and depositional effects, displays characteristics as follows:high supply of detritus source, high abundances of Ti, Fe, Al, Na, K, Co, Cr, Cd and Mn, low content of carbonate rocks, Ca elements and sapropel group, and great variations in sedimentary structures and paleoenvironmental indicators of scour surface and cross-bedding which represent strong hydrodynamic conditions. Parasequence group often represents a process of large scale progradation and retrogradation, with great value segment of TOC or Sr corresponding with the transformed surface. Due to small particles, slow deposition process, and abundant organic matter, the fine-grained sediments have strong adsorption on K, U, Th and other radioactive elements, which contributes to the enrichment of these radioactive elements, and better performance of GR logging on fine shale resolution than other lithologies. The GR logging response bears obvious longitudinal regulationand is of good contrast tracking feature on the Es₄s-Es₃x of Jiyang Depression, so we can use the vertical evolution of GR curve to contrast and trace the fine-grained sedimentary sequence in the whole region.

A Study on Microscopic Pore Characteristics of Tight Reservoir of Chang 7 Sedimentation Section of Yanchang Formation, Ordos Basin

ZHANG Zhongyi, CHEN Shijia, YAO Jingli, LIU Xin, ZHAO Yingquan

2016, 38(6):  70-80.  DOI: 10.11885/j.issn.1674-5086.2015.05.01.02

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There lacks systematic research into the complex characteristics of tight oil reservoir in Ordos Basin. By means of core observation, test data analysis, constant speed mercury injection experiment, field emission and CT scanning etc., we studied the formation and characteristics of Chang 7 tight oil reservoir. The research suggests that tight oil reservoir consists of tight sandstone formation of traction current and gravity flow deposits of Chang 7 section of Yanchang formation, which is of poor reservoir property with fine granularity, thick reservoir, high brittleness,. Pore types are mainly intergranular pores and feldspar dissolved pores which are mainly micro-nano-scale pores with flake-shaped and tube-shaped throats; due to the filling of clay minerals and organic matter, effective pore volume is small, but micro cracks are highly developed and are of good connectivity; lower limit of oil reservoir physical property is low, and fluid saturation is high.

Recognition of Accretion of Sand Bodies in Single Mouth Bar Based on Horizontal Well Data

ZHANG Rui, LIAO Xinwu, LIU Zongbin, ZHANG Xuefang, SI Shaohua

2016, 38(6):  81-89.  DOI: 10.11885/j.issn.1674-5086.2015.12.23.01

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A distant well spacing is often allocated for offshore oilfield due to the geographical restrictions. Consequently, the characterization of such underground reservoir structures with the current overlay method for multi-well models used mainly under dense-well pattern conditions usually achieves a poor precision. Therefore, based on a large number of horizontal well data of X Oilfield in Bohai Bay, we did the research on characterizing such debouch bar reservoir structures:Horizontal section which is always drilled in the inner debouch bar can meet the debouch bar accretion sand bodies when drilled laterally. So, we used the scale statistic data of the drilled accretion sand bodies to guide the characterization of accretion sand bodies. With using the method in X Oilfield in Bohai Bay, it shows that the length of horizontal interval is always between 240-320 m, and there are 3-6 stages of lateral accretion interbed (overlay surface). This study has not only a significantly economic value in efficiently developing reservoirs of offshore oilfield where there is a lack of multi-well models data and test data, but also guiding significance for similar onshore oilfields in characterizing lower level structure elements.

Application of Imaging Logging Data to the Structure Interpretation of Carboniferous Formation

CHEN Liang, ZHAO Yiqing, QIN Jianhua, QU Huailin, DONG Haihai

2016, 38(6):  90-96.  DOI: 10.11885/j.issn.1674-5086.2015.06.01.14

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The carboniferous structure is very complicated in the northwest of Junggar basin. It makes the research on the structure in this area difficult by the seismic and diplog interpretation for its diverse lithology and well-developed fracture. For those reason, the seismic and diplog data quality is poor. The downhole true formation occurrence can be provided directly with imaging logging. Furthermore, the structure shapes can be finely interpreted with logging data. The paper aimed at dividing the lithological layer of the volcanic layers and interpreting the true formation occurrence by the imaging characteristics. Finally, the structure of volcanic is dissected according to the regular pattern of multi-well stratigraphic occurrence, founding that there are two reverse faults in this complex steep structures area.The result shows that the new method of the interpreting of structure of volcanic reservoir is effective.

Fracture Development Characteristics and Its Influence on Development in Q4 Member of Fuyu Oilfield

TANG Xiaoyan, LI Pan

2016, 38(6):  97-104.  DOI: 10.11885/j.issn.1674-5086.2015.07.16.22

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In the process of water injection development, the water breakthrough of natural fracture has strong universality and directivity. Accurate identification of the occurrence of natural fracture, especially the fracture distribution characteristics of oil enrichment area, therefore, is the key to the improvement of water injection recovery for high water-content fractured low permeability oilfield. This paper makes full use of existing pressure coring and dynamic development data, systematically analyzes the distribution characteristics of natural fractures in the studied area, and studies the influence mechanism of fracture on water flooding development. The study results show that small size, high angle fractures with short extension are highly developed in Fuyu oilfield, with east-west fracture direction. Therefore the injected water will rapidly fill the east-west fractures, and water channeling will occur. This results in the water flooding and shut-in of oil wells in east-west direction, and the remaining oil is formed between east-west oil and water wells; the volume sweep efficiency of injected water in east-west direction is small, and the water flooding effect is poor.

Researches on Nitrogen Foam Flooding Technology in the Tahe Triassic Sandstone Reservoir

LIU Xueli, HU Wenge, TAN Tao, ZHANG Linyan, LIU Rui

2016, 38(6):  105-110.  DOI: 10.11885/j.issn.1674-5086.2015.01.19.02

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Compared with other sandstone reservoirs in China, the Tahe triassic sandstone reservoir is a block bottom water reservoir, which is characteristic of deeply buried reservoir, active bottom water, high formation temperature and high salinity(excessive calcium and magnesian ion). Therefore the number of low production and low effectiveness wells is increasing when the oil wells are flooded in the middle-later developed period. In addition, the chemical flooding to improve oil recovery does not apply due to high temperature and high salinity. Based on the researches on enhanced oil recovery technology in sandstone reservoir and the practical characteristics of bottom water sandstone reservoir of Tahe Oilfield, nitrogen foam flooding experiments were made and the feasibility was proved. Then the pilot test on field was conducted, and it showed that the nitrogen foam flooding technology is an effective method of improving oil recovery in bottom water sandstone reservoir.

The Outlook for China's Tight Oil Reservoir Stimulation Concept and Technology

ZHAO Liqiang, MU Mei, LUO Zhifeng, LIU Pingli, ZOU Dongli

2016, 38(6):  111-118.  DOI: 10.11885/j.issn.1674-5086.2015.03.25.21

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China has tremendous unconventional tight oil resources which are widely distributed in lots of petroliferous basin. However, unlike those in North-America, all the tight oil reservoirs discovered in China belong to continental sedimentation, with interbedded formation, worse reservoir physical properties and less oil reserves per unit volume, which makes it much harder to stimulate. Due to the limitation of stimulation technology and concept, there is no large-scale exploitation of China's tight oil reservoirs. To solve this problem, based on the thorough analysis of successful stimulation experience in North-America, and combined with the characteristic of China's tight oil reservoir, stimulation difficulty was analyzed and development direction of large-scale exploitation was discussed. Analysis showed that the critical factors of successful stimulation in foreign tight oil fields were the better stimulation formation condition and the application of fast drilling technics and multi-stage and multicluster fracturing technics. Researchers should continue researches about geomechanics and extension mechanism, etc, break through the inertial thinking, explore new stimulation patterns, learn and digest international advanced technology, and establish agent technology suitable for China's tight oil reservoirs, so as to realize large-scale exploitation with the minimum cost and the maximum effect.

Interlayer Interference Evaluation by the Recovery Rate Interference Factor for the Waterflooding Oil Reservoir in the Medium-late Period

XIE Yiting, CHEN Zhaohui, CHAI Xiaoying, JI Yun

2016, 38(6):  119-124.  DOI: 10.11885/j.issn.1674-5086.2015.11.11.25

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Pressure between payzones that connect the production or injection wellbore will be balanced automatically. This process will deplete production degree of each layer but increase difference of pressure and fluid distribution of each layer for water flooding reservoirs. In the Medium-late period after Overall Development Plan(ODP), the real-time adjustment or modification were required since the ODP may not be the best as long as more and more static and dynamic information from reservoir has been put into the reservoir model. In addition, the performance of interlayer interference will keep changing following in-situ stress and fluid distribution during production and injection development procedure. It is obvious that criteria are required to make the reasonable infill and strata subdivision plan in the medium-late development phase. In this study, the interlayer inference was evaluated by the oil recovery rate interference factor with productivity and reserves and was defined as the ratio of oil recovery rates between commingling payzones. Furthermore, the analysis charts were calculated by numerical simulation to evaluate the balanced level of commingling multilayer reservoir development. The results indicated that production rate adjustment can fix lower level unbalanced development due to minor interlayer interference phenomena and strata subdivision is required during higher heterogenous waterflooding. Results show the best development performance would be the equal oil recovery rate between each commingling payzones.

Study on Diamond Inverted Nine-spot Well Pattern Reasonable Well Spacing for Planar Anisotropic Reservoir

LIU Feng, CHEN Xiaofan

2016, 38(6):  125-130.  DOI: 10.11885/j.issn.1674-5086.2013.11.18.03

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Reservoir anisotropy permeability has an important effect on the well pattern and oil well capacity during the oilfield development process. However, the normal well pattern is not suitable for the anisotropic reservoir, and the oil well water breakthrough time in the main permeability direction is short. However, the water flooding in the side permeability direction is poor or the oil well is not swept. In order to solve this problem, we break through the traditional well pattern, based on the water flooding stream tube method and material balance equation, and build up the nine spot well network of planar anisotropic reservoir. In this paper, when the water breakthrough time of edge well and corner well is equal, the reservoir can achieve the balance flooding effect. According to the basic characteristics of anisotropic reservoir, this paper establishes the calculating formula of geometric parameters of reasonable injection and production unit of nine spot well network. And the formula is verified by examples. In the anisotropic reservoir, the shorter corner well spacing increases with the increase of the longer corner well spacing and decreases rapidly with the increasing anisotropy coefficient. When the anisotropic coefficient is smaller than 10, the corner well spacing decreases slowly. The new diamond inverted nine-spot well pattern improves reservoir recovery and sweep efficiency of injected water. This paper provides the theoretical basis and guidance for planar anisotropic reservoir construction of nine spot well pattern.

Simulation and Optimization of Downhole Gas-Liquid Separator at Low Liquid Rate and High GLR Wells From CO₂ Flooding Reservoir

LIU Yonghui, ZHANG Nan, PAN Ruosheng, ZHANG Deping, WANG Wubing

2016, 38(6):  131-137.  DOI: 10.11885/j.issn.1674-5086.2014.12.15.03

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CO₂ flooding technology was well applied in low permeability reservoirs in Jilin Oilfield, where production wells are characterized by small liquid rate and high gas liquid ratio, which has a serious effect on the sucker rod pump system, such as low pump efficiency. Aiming at dropping the gas rate pumped into sucker rod in those wells, we developed a new downhole gas-liquid separator on the basis of gas separation principle of the conventional gravity type gas anchor and that of spiral gas anchor. In this paper, CFD is improved to optimize its parameters. Suspended point motion of pump unitsis taken as boundary conditions of the motion pump, the surface gas-liquid ratio is replaced by the gas-liquid ratio and bubble breakage and aggregation are taken into consideration. The swabbing parameters of sucker rod pump were selected to get its high efficiency. The new downhole gas-liquid separator was installed at Well X. The casing pressure dropped from 9.5 MPa to 0.4 MPa, daily liquid production rate increased from 1.5 t/d to 17.4 t/d, and the pump efficiency was 84.6% when the daily gas volume rate is 792 m³/d. Its pump efficiency is higher than the average pump efficiency of 40.1% of other wells in the same block. The study has important practical significance in application of CO₂ flooding and has an important reference in similar high gas liquid ratio wells with sucker rod pump.

Method for Water-Flooded Layer Evaluation in Extra-Low Permeability Reservoir in WY Block of AS Oilfield Flooded by Fresh-Water

HUI Gang, WANG Youjing, YAN Linhui, LI Jiahong, LIU Li

2016, 38(6):  138-146.  DOI: 10.11885/j.issn.1674-5086.2014.08.07.02

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The formation water is of extremely high salinity in the extra-low permeability reservoir in WY Block of AS Oilfield. After the long term water-flooding, the oil layer resistivity curves display an asymmetric U-Type and the resistivity of severely water-flooded oil layer exceeds that of original oil layer. The traditional logging evaluation approach for medium-high permeability reservoir does not apply to extra-low permeability reservoir, owing to the complicated factors of water flooding in the extra-low permeability reservoir and reservoir characteristics. The rock-electric experiment is carried out under the simulated reservoir conditions to indicate the logging mechanism of water flooding in the extra-low permeability reservoir. The resistivity value of water-flooded oil layer depends on the resistivity ratio between injection water and formation water. On the basis of logging data and core analysis, formation water salinity and SP, RT, AC logging data, the water-flooded oil layer can be identified and the mixed formation water resistivity can be obtained. The logging interpretation model is finally built up for the water-flooded layer and matches well with the actual production data.

Effect of Pre-Wetting on Pipeline Wettability

XU Daozhen, ZHANG Jinjun, WANG Bin, ZHANG Guozhong

2016, 38(6):  147-151.  DOI: 10.11885/j.issn.1674-5086.2015.06.10.01

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In view of the problem of oil pipeline inner wall corrosion, by the measurement of the contact angle of acrylic and steel surface, we carried out to study the effect of inorganic salt icon, solid surface roughness and pre-wetting history on oil-water-solid system. The results indicate that the carbon steel mainly appears hydrophilic, while the acrylic mainly appears hydrophobic. On the surface of both materials, the pre-wetting phase always inclines to prevent the solid surface wetted by another phase, and the increasing icon concentration enhances the hydrophilic of the solid surface. Both of the phenomena are more obvious on the carbon steel surface. What is more, pipeline material affects not only the final contact angle, but also the wetting process, which shows that wetting requires much longer time to reach balance on the carbon steel than on the acrylic surface, which may exert an effect on the distribution of corrosion in the pipeline.

Establishment and Application of a New Method for Predicting Polymer-Flooding Development Potential

YANG Shengjian, LIU Zhaoxia, WANG Qiang, GAO Ming, LIU Wanlu

2016, 38(6):  152-157.  DOI: 10.11885/j.issn.1674-5086.2015.09.02.21

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By analyzing the influence degree of main factors on polymer flooding effect, the classification and weighting coefficient for each factor were determined. A comprehensive scoring method for polymer flooding was established with consideration of reservoir parameter scores and their weighting factors. The comprehensive scores of 13 polymer flooding field tests in China were calculated by the new method. A relationship between EOR and polymer flooding comprehensive score coefficient was built by exponential regression according to the evaluation result of polymer flooding field tests in China. It could be used to predict the development effect of polymer flooding for different reservoir types. It was applied to prediction of the EOR of polymer flooding in Gucheng 124 Block and Xiaermen H2II Block. The errors between the predicted results and actual values were 3.8% and 12.7% respectively. It was objective and convenient to calculate the polymer flooding potential and evaluate the polymer flooding feasibility in the fields.

Corrosion and Inhibition Performance Study of Oil Casing Steel in Calcium Chloride Solution

HUANG Qiuwei, JIAN Lu, LI Guoliang, DU Zonghe, WANG Xu

2016, 38(6):  158-163.  DOI: 10.11885/j.issn.1674-5086.2015.02.04.04

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In order to know the corrosion resistance of ordinary carbon steel in the regular killing fluid and find a way to control its corrosion condition, weight loss method and electrochemical methods were used to study N80 and P110 steel's corrosion situation and corrosion inhibition ability in 1.35 g/cm³ CaCl₂ solution at standard pressure and different temperatures, high temperature and pressure, and different types of corrosion inhibitor, dosage. The experimental results showed that with increasing temperature the corrosion of N80 and P110 steel is intensified. And at the standard pressure with the temperature range of 60~80℃, the corrosion current density of the ordinary carbon steel raised from 10^-6 A/cm² to 10^-5 A/cm². At 4 MPa with temperature rising from 90℃ to 150℃, the corrosion rate increased an order of magnitude. At 80℃ with the amount of WLD31A 30 mg/L, it improved inhibition efficiency on N80 up to 95.51%, and that on P110 up to 93.11%. Within the range of 60~80℃, elevated temperatures help to improve WLD31A inhibition effect, the inhibition efficiency of N80 increases from 88.08% to 95.51% and P110 from 61.38% to 93.11%.

Numerical Simulation of Cuttings Pulse Carrying in a Horizontal Well

ZHU Xiaohua, CHEN Keyu, MAO Yu, LIU Biao

2016, 38(6):  164-171.  DOI: 10.11885/j.issn.1674-5086.2015.01.14.01

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Horizontal well drilling technology has become an important means of modern oil and gas exploration and development. It can cause some dangerous accidents, such as high friction and torque, stuck pipe and choke pumps, when the annulus transportation condition of horizontal well is poor. And the accidents will impact the life of drilling tools and the safety of drilling progress, which cannot be solved in conventional technology. So, the method of pulse carrying cuttings is extremely needed. On the basis of the existing hydraulic pulse and the following diversion mechanism, a slimhole horizontal well flow model is established. It uses RNG k-ε model, the power-law model and the secondary development of subroutines for numerical calculations to determine reasonable pulse cycle of pulse carrying rocks, duty cycle, and other parameters. In order to find the distribution law of the velocity and density of cuttings it also discusses the effect of the flow rate of drilling fluid, the eccentricity of drilling pipe and the diameter of cuttings. The results show that under the same condition, pulse carrying cuttings is more efficient, destroying cuttings better and reducing cuttings bed concentration by about 40%.

Mechanical Study of Completion String With Multi-packer for High Pressure Gas Wells

ZHANG Zhi, WANG Bo, LI Zhong, LI Yanjun, ZHANG Chao

2016, 38(6):  172-178.  DOI: 10.11885/j.issn.1674-5086.2015.10.27.21

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The string with multi-packer, which is recommended by Norsok D010 standard, is an important type of high temperature high-pressure completion string. However, compared with the single packer, the force and deformation of completion string with multi-packer are more complicated, and the local trap pressure does great damage to pipe string. Therefore, the mechanical model with consideration of the end effect, deformation effect and effect of thermal expansion and contraction as well as helical and sinusoidal buckling effect was established. Besides, calculation based on field condition was performed. The results indicate that the force and deformation of string are greatly affected by the packer depth and wellhead temperature and pressure, and effect of multi-packer on mechanical behavior of string should be considered in the string design and evaluation.