, Volume 38 Issue 5

    

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油气勘探
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  Accumulation threshold and exploration potential of deep basin oil in the Songliao Basin

  Hou Qijun; Zhao Zhanyin and Huang Zhilong

  , 2011, 38(5): 1965-0.

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  In order to further understand the accumulation mechanism and distribution rules of deep basin oil, the laboratory physical simulation experiment for water-seal-oil in sand columns with different grain sizes was conducted, and the water-seal-oil mechanism and the accumulation threshold of deep basin oil were analyzed. Stable deep basin oil can be formed under laboratory conditions. The accumulation threshold of deep basin oil mainly depends on the pore throat radius of oil-bearing sand layer as well as the oil/water interfacial tension and strata dip under such conditions. The accumulation threshold and its main controlling factors of the deep basin reservoir in the Fuyang oil layer were studied, and the prediction model of deep basin reservoir boundaries was established: the porosity is less than 11%, the permeability is less than 1×10－3 μm2, the largest pore throat radius is less than 6.2 μm, and the burial depth is 1800–2100m, which was located at the lower positions of syncline or slope, and good source rock in Qing-1 Member was developed, with obviously abnormal pressure. Three “sweet spot” areas favorable for deep basin oil in the Songliao Basin were determined, namely south Liangjing area, east Haituozi area and west Qian’an area. The predicted deep basin oil potential in these three areas was 0.317 billion tons. The total proved resources of deep basin oil in the Songliao Basin were 1.575 billion tons, with good exploration potential.
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  Geological exploration theory for large oil and gas provinces and its significance

  Zhao Zhengzhang; Du Jinhu; Zou Caineng and Hu Suyun

  , 2011, 38(5): 1968-0.

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  In the period of “11th Five-year Plan”, PetroChina proposed and developed the geological exploration theory for large oil and gas provinces, under which a group of major discoveries have been achieved. Large oil and gas provinces are large oil/gas-bearing areas consisting of several groups or belts of reservoirs (oil/gas fields) under the same large structural setting, which are determined by similar accumulation conditions, dominated by a certain type of hydrocarbon reservoir, and overlaid vertically and connected horizontally. The combination of large structural setting, favorable source rock, and widely distributed heterogeneous reservoir is essential for development of large oil and gas provinces. Large oil and gas provinces are mainly developed in large structures such as continental depression, foreland basin and marine craton basin, with large oil/gas-bearing area and considerable reserves. Oil and gas pools are mostly a single type. Reservoirs are widely distributed, with low porosity and low permeability and high heterogeneity. Hydrocarbon distribution is not controlled by local structures and there is no uniform oil/gas/water contact but varying properties of oil, gas and water. Based on the reservoir lithology, large oil and gas provinces are divided into clastics, carbonates and volcanics, which are subdivided into five sub-large oil and gas provinces, i.e. low porosity and permeability clastic, foreland complex, steep and deep structure, carbonate karst formation, carbonate platform margin reef, and volcanic formation. Moreover, key technologies integrating seismic survey, drilling, logging and formation test have been developed. The exploration in large oil and gas provinces stresses the concept of “overall study, overall exploration and overall control”, and the evaluation method of “integrating exploration and development, and integrating production expansion and reserve growth”, to maximize the benefits of both exploration and development.
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  Hydrocarbon formation and accumulation of the deep Palaeogene of the Jiyang Depression

  Zhang Linye; Xu Xingyou; Liu Qing; Kong Xiangxing and Zhang Shouchun

  , 2011, 38(5): 1969-0.

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  Using geochemistry, sedimentary and petroleum geology methods, and based on the analysis of spatial distribution of deep source rocks and sedimentary organic facies, the favorable exploration prospects in the Jiyang Depression，Shengli Oilfield are discussed, showing that there are 4 types of sedimentary organic facies (including anoxic organic facies, anaerobic organic facies, dysaerobic organic facies and aerobic organic facies) in deep source rocks of Kongdian Formation - Sha-4 Member, Palaeocene. Anoxic facies and anaerobic facies source rocks are discovered in the Sha-4 Member and are proved as excellent source rocks, while the Kongdian Formation source rocks are composed mainly of the dysaerobic facies and aerobic facies, as common source rocks. The whole hydrocarbon expulsion process is divided into 3 stages, including free water expulsion, hydrocarbon generation and energy accumulation, and hydrocarbon expulsion from microfractures. The hydrocarbon expulsion from deep source rocks mainly occurs in the stage of hydrocarbon expulsion from microfractures, when there are three oil and gas migration modes under different geologic conditions, including vertical migration, lateral migration and downward migration. The studies indicated that the hydrocarbons in shallow and medium formations from the Sha-4 Member excellent source rocks of anoxic and anaerobic facies are mainly accumulated through vertical migration along the faults, while the reservoirs formed by lateral migration and downward migration have not been revealed. It is potential in the deep Palaeocene of the Jiyang Depression.
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  Structural superimposition-and-conjunction and its effects on hydrocarbon accumulation in the Western Sichuan Depression

  Li Zhiwu; Liu Shugen; Chen Hongde; Sun Dong; Lin Jie and Tang Cong

  , 2011, 38(5): 1970-0.

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  Records of unconformities and lithologic facies and analysis of paleo-structure show that at least 11 tectonic boundaries exist in the Meso-Cenozoic continental strata in the Western Sichuan Depression. Affected by the Longmenshan thrust belt on the west side, Micangshan structural belt on the north side and Chuandian structural belt on the southwest side, NE-trending, sub-EW-trending and sub-NS-trending structures were developed correspondingly in the Western Sichuan Depression. The NE-trending structures were developed to different degrees in most tectonic movements, while the sub-EW-trending and sub-NS-trending structures were formed in the Yanshanian and Himalayan, respectively. The three groups of structures were superimposed by one another in multi-stage tectonic movements, producing mainly five types of structural complexes, i.e. coaxial superimposition, orthogonal superimposition, oblique superimposition, multi-direction superimposition and structural conjunction. Structural controls on hydrocarbon accumulation in the Western Sichuan Depression can be expressed as the following three aspects, i.e. timing, locating and modification. Hydrocarbon distribution and the formation of primary gas pools were mostly controlled by early structures (in the Indosinian and Yanshanian), whereas late structures (mainly in the Himalayan) only had modification effects on early gas pools, resulting in structural displacement, reservoir improvement, the destruction of primary gas pools and the formation of secondary oil pools. Accurate reconstruction of the Indosinian-Yanshanian paleo-structures and fracture behaviors during the multi-stage and multi-direction structural superimposition are two important aspects that need to be paid more attention to for the future hydrocarbon exploration in this region.
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  Diagenesis of deep sandstone reservoirs and a quantitative model of porosity evolution: Taking the third member of Shahejie Formation in the Wendong Oil field, Dongpu Sag as an example

  Wang Ruifei and Zhao Liangjin

  , 2011, 38(5): 1971-0.

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  The diagenesis and porosity evolution in the deep 3rd member of Shahejie Formation of the Wendong oil field was analyzed using thin-sections, casting thin-sections, X-ray diffractometry, scanning electron micrograph observations, and other data. Sandstones are currently at the late diagenetic period. The pore types consist of primary pore and the inter-granular dissolved pore and intra-granular dissolved pore of feldspar, debris and carbonate cements. The physical property are mainly controlled by carbonate cementation and dissolution, and distribution of abnormally high fluid pressure. The evolution of porosity parameters shows that primary porosity is 36.75%, the porosity loss rate is 40.49% during the process of mechanic compaction, the porosity loss rate is 37.25% during the process of cementation and metasomasis, and the porosity increase rate is 17.88% during the process of dissolution. The proportion of primary porosity is 55.03%, and that of the secondary porosity is 44.97%. The error rate in the quantitative study of porosity is 0.96%, and the main influencing factor of error rate is sorting coefficient of detrital rock (So).
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  Structural characteristics and petroleum exploration potential in the deep-water area of the Qiongdongnan Basin, South China Sea

  Lei Chao; Ren Jianye; Li Xushen; Tong Chuanxin; Yin Xinyi and Min Hui

  , 2011, 38(5): 1972-0.

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  According to analysis of the newly acquired high-quality seismic reflection data, the Qiongdongnan Basin is divided into three first-order structural units, i.e. northern uplift, central depression, and southern uplift. An NW-trending graben and horst belt is identified, showing that the structural framework of the basin is characterized by zones in the north-south direction and blocks in the west-east direction.. A detailed interpretation of geological structures and quantitative analysis of faulting is carried out on No. 2 fault system, which is an important boundary marker between the northern uplift and the central depression. Results indicate that No. 2 Fault is characteristic of segmented faulting. The structural characteristics of sags in each structural unit is studied and the sags are classified into three types, half-graben, graben, and compound graben, which are further divided into ten subtypes. On the basis of the structural unit classification, along with existing geological data and exploration achievements, it is believed that the petroleum exploration potential is good in the structural units of the basin.
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  Lithologic reservoirs in Block A in the South Turgay Basin, Kazakhstan

  Yin Wei; Zhang Mingjun and Kong Linghong

  , 2011, 38(5): 1973-0.

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  Block A in the South Turgay Basin, Kazakhstan, lies in a gentle slope zone of rifted lake basin, where structural traps are not developed, so it is important for explorers to find litho-stratigraphic reservoirs. The drilling records show that, in Block A, the lithologic reservoirs are in the Jurassic System, containing 5 formations from bottom to top: Aybolin, Doshan, Karaganshy, Kumkol and Akshabulak. Through the research on Jurassic reservoirs, source rocks and reservoir-seal assemblage, it is proposed that there are three types of lithologic reservoirs at target formation: reservoirs with sands updip and pinch-out at front of slope zone, reservoirs with isolated sands in underwater distributary channels, and reservoirs with isolated sands at mouth bar. Well A12 is discovered containing middle-porosity middle-permeability reservoir with sands updip and pinch-out at front of slope zone, which was affected jointly by self generation - self preservation and lateral migration of hydrocarbons. The comprehensive analysis of accumulation conditions shows that the effective reservoir-seal assemblage is the main controlling factor for accumulation. With several geological and geophysical methods, it is concluded that the prospects are lied in central and west parts of Block A.
油气田开发
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  Adaptability of a deep profile control agent to reservoirs: Taking the Lamadian Oilfield in Daqing as an example

  Lu Xiangguo; Wang Shuxia; Wang Rongjian; Wang Hongguan and Zhang Song

  , 2011, 38(5): 1974-0.

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  As the Lamadian Oilfield in Daqing features thick layers, complex and various facies combinations, and serious interlayer heterogeneity, the influential factors of a deep profile control agent on deep profile control and oil production increase and its adaptability to reservoirs were studied with core flooding tests. The results showed that, the amount, intensity and permeability variation coefficient (VK) of reservoir all influenced the effect of oil production increase after profile modification. The larger the injected volume, the better the stimulation effect. The increment of recovery ratio showed an increase and then decrease trend when agent intensity increased. The larger VK resulted in better stimulation effect. Core flooding tests and instrument detection results showed that, the profile control agent can flow in the pore only when the values of molecular group size and medium value of pore throat radius were in the compatibility zone. Therefore, for the heterogeneous reservoir, the characteristics of high, middle, and low permeability layers and match relations of agent molecular group size and medium value of pore throat radius of reservoir rock must be taken into consideration when designing the agent intensity and slug so that the damage to the middle and low permeable layers can be reduced as much as possible
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  Characteristics and causes of Mesozoic reservoirs with extra-low permeability and high water cut in northern Shaanxi

  Wang Jianmin; Liu Shengfu; Li Jun; Zhang Yongfu and Gao Ling

  , 2011, 38(5): 1976-0.

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  Combining with actual oil field development, based on comprehensive analysis on the oil production and oil test data, this paper summarizes the characteristics of the Chang 6 reservoir of extra-low permeability and high water?cut?in the Weijialou oilfield in northern Shaanxi and the distribution rule of high water cut zones. The results show that the Chang 6 reservoir in the Weijialou oilfield belongs to a typical reservoir with extra-low permeability and high water cut, its water cut contour shows irregular annular distribution around local structure highs in plane. The water cut distribution within the reservoir shows high heterogeneity; along the NE-SW direction, water cut change was relatively stable, water cut contour extending in band shape; along the NW-SE direction, water cut fluctuated greatly, contours showing an alternating distribution of high and low water cut zones; there exists high water cut zone out-thrusting locally. Lack of effective hydrocarbon source rocks and poor resources conditions are the underlying causes of high water cut in the Chang 6 extra-low permeability reservoir in the Weijialou oilfield. High crude oil viscosity, large difference of fluid properties, high fluidity ratio, and well developed natural fractures are the main internal cause of high water cut.
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  Stability model of borehole wall during the well test after acidizing treatment

  Qiu Kang; Chen Mian; Jin Yan and Zhang Fuxiang

  , 2011, 38(5): 1977-0.

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  In the DB Block, Tarim, wellbores collapsed during well test after sandstone matrix acidizing. Aimed at this issue, the parameter variation rule of rock mechanics are studied through experiments. The models of mechanics parameters during acidizing are established. The stress distribution around wellbore with acid treatment is described, taking plastic zone into consideration. The evaluation method of wellbore stability with acid treatment is established. The research indicates that, the acidizing treatment would bring into changes in Young's modulus, Poisson’s ratio, cohesion and internal friction angle. During the acidizing, the change of Young’s modulus and Poisson’s ratio can be worked out through variation of porosity. Decrease of cohesion and internal friction angle can be fitted through experimental data. The acidizing treatment could lead to stress decrease, which is determined by acidizing time and effective acidizing radius. The wellbore stability is determined by the decreased stress and rock strength. In general, the effect of acidizing treatment at an earlier period on wellbore stability is greater than that at a later period.
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  Development techniques for horizontal wells in low permeability reservoirs, Jilin Oilfield

  Zhao Jing

  , 2011, 38(5): 1978-0.

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  Aimed at the development situation for horizontal wells in low permeability reservoirs in the Jilin Oilfield, evaluation standards are established for the geological parameters of horizontal well adaptability in lower permeability reservoirs. According to different permeability grade, eight blocks of two kinds, suitable for the development with horizontal wells, were selected. Take M block, N block, and E block as examples of reservoir development with horizontal wells. 5 aspects, including, fine geological description, parameter optimization of reservoir engineering, optimization of production and injection program, horizontal well trajectory control, and energy supplement are researched on horizontal well reservoir engineering optimization design. Reservoir engineering design parameters adapting to geologic characteristic of the Jilin Oilfield are given and a series of horizontal well development techniques is formed. Different energy supplement programs in N block are researched by Eclipse numerical simulation software. The cumulative production of horizontal well reaches the peak when water injection in vertical well locates in the toe of horizontal well. The horizontal well application result in M block shows that the cumulative production of horizontal well is 2.5 times that of vertical Well 130-6 around at the same period.
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  CO2 and viscosity breaker assisted steam huff and puff technology for horizontal wells in a super-heavy oil reservoir

  Li Zhaomin; Lu Teng; Tao Lei; Li Binfei; Zhang Jiguo and Li Jing

  , 2011, 38(5): 1979-0.

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  In order to improve the recovery effect of steam huff and puff in a super-heavy oil reservoir, the displacement efficiency of CO2 and viscosity breaker assisted steam flooding was studied through in-lab displacement experiments. The viscosity reduction mechanism of CO2 and viscosity breaker assisted steam huff and puff for horizontal well was realized by numerical simulation. The results show that the displacement efficiency of CO2 and viscosity breaker assisted steam flooding (80.8%) is higher than that of steam flooding (65.4%). The CO2 and viscosity breaker assisted steam huff and puff technology for horizontal well realizes the rolling replacement of synergistic viscosity reduction of viscosity breaker, CO2 and steam, thus effectively reducing the steam injection pressure, expanding the steam sweep area, i.e., expanding the viscosity reduction region, and improving oil production rate. It could be divided into four compound viscosity reduction areas with the difference of temperature distribution and viscosity reduction mechanism. They are steam compound viscosity reduction region, hot water compound viscosity reduction region, low temperature water compound viscosity reduction region and CO2-viscosity breaker compound viscosity reduction region. Field tests show that the CO2 and viscosity breaker assisted steam huff and puff technology for horizontal well is good at reducing viscosity and improving production of super-heavy oil reservoirs with deep and thin layers, deep and heavy layers, shallow and thin layers.
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  Design optimization for the horizontal well pattern with herringbone-like laterals

  Zhang Shiming; Zhou Yingjie; Song Yong; Wan Haiyan; An Yongsheng and Xu Qiang

  , 2011, 38(5): 1980-0.

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  For the configuration design of herringbone wells, we applied a coupled multi-segment well model to determine the design principles of different parameters, and also made evaluation of the sensitivity for each parameter by orthogonal design. The results show that the factors influencing productivity of herringbone wells are mainly those of layout (location, sides and symmetry) and morphology (length, quantity, angles and spacing) for laterals. The order of morphology parameters influencing on the production of herringbone wells is as follows: length > number > angle > spacing for laterals. The design principles of the configuration of herringbone wells are: different sides, asymmetric, the laterals should be put as near as possible to the ends of the main wellbore, the number of laterals should be not least than 2, and the angle should be more than 30 degrees. The actual engineering capability should be considered in practice. With this method, three herringbone wells in the Shengli Oilfield were applied to calculate the productivity, and all the errors were less than 3%. The designed BO2 well of the Bajiaoting reservoir which was located in the Pinghu oil and gas field of East China Sea had a productivity of 350 m3/d.
石油工程
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  Spudcan bearing capacity calculation of the offshore jack-up drilling platform during the preloading process

  Zhang Puyang; Yu Xiaoyang and Ding Hongyan

  , 2011, 38(5): 1981-0.

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  To predict the penetration depth of the offshore jack-up drilling platform during the preloading process, the fluid-solid coupling theory was introduced. The limited element model of the earth-spudcan system under saturated clay was established. With this model, the spudcan bearing capacity coefficient was numerically calculated when spudcans penetrating into homogeneous and heterogeneous clay. The result showed that, the spudcan bearing capacity coefficient is mainly decided by the earth strength and spudcan penetration depth, as for earth with lower strength heterogeneous coefficient, the spudcan bearing coefficient has a positive correlation with the spudcan penetration depth, while for earth with higher strength heterogeneous coefficients, the correlation is negative. When the spudcan penetration depth is about 20 m, the maximum bearing capacity coefficient of spudcan is 10.30 (not consider earth backflow) and 12.25 (consider earth backflow), respectively. The calculation method for spudcan bearing capacity during the preloading process was given. With this method, the penetration depth of spudcan under certain earth condition for the 5th platform in the Bohai Sea was calculated. Because the proposed calculation method considered the influences of reaction between earth and spudcan, the nonlinear property of earth, end resistance at the bottom of spudcan and lateral resistance of spudcan during the whole preloading process, thus the predicted spudcan penetration depth is more reasonable, and has the difference of about 20% with the result of traditional calculation method.
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  Computer aided designs for offshore pipe S-laying

  Bai Ning and Zhao Dongyan

  , 2011, 38(5): 1982-0.

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  In the traditional offshore pipe S-lay design, the modeling and configuration parameters adjustment of firing line are completed by manual way. However, the traditional design method costs a lot of time and labors, and can not work with stingers with complex structures. This paper has illustrated a program developed to aid offshore pipe laying design. This program can provide precise model for any type of stinger of firing line with any geometry and calculate roller supports coordinates automatically with optimized configuration. The program adopts finite element method to solve static offshore pipe S-lay problems, conducts analysis to calculation results and selects the best configuration parameters of firing line. The whole design procedure can be completed automatically by this software. With the method described in this paper, the efficiency of design increases greatly, which has significant value in offshore pipe laying design area. A real example of a stinger with two sections shows that labor and cost are decreased by 88%, and the new methods can work with complicated stingers with even three or more sections, which cannot be realized with manual method. The new method improves the design quality and optimizes the design result.
综合研究
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  Types and characteristics of chert reservoirs in oversea petroliferous basins

  Lu Fang; Liu Jiaqi; Li Yahui; Liu Zerong; Zhou Yan and Ding Weixing

  , 2011, 38(5): 1983-0.

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  Combining with the actual exploration and production of oil and gas in cherts in foreign countries, this paper describes the origin, composition and classification of cherts and discusses the trap type, reservoir nature, petrophysical features of chert reservoirs and problems met in drilling, completion and production processes. Cherts are silica-rich rocks formed by biological, chemical, biochemical, and volcanic processes. They are tight, hard and brittle. Traps of chert oil and gas reservoirs can be divided into six types, fractured, weathering crust, hydrothermal, self-generatin and self-storage, hydraulic, and lateral barrier. Chert reservoirs are heterogeneous and porosity and permeability are controlled by rock facies, muddy content, and pore nature, among other factors. Study shows that cherts are excellent reservoir rock and can form oil and gas reservoirs under a good association of source, reservoir and seal. They are important target for lithological reservoirs of oil and gas.
学术讨论
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  Effect of confining pressure on mechanical behavior of methane hydrate-bearing sediments

  Li Yanghui; Song Yongchen; Yu Feng; Liu Weiguo and Wang Rui

  , 2011, 38(5): 1984-0.

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  Synthesized gas hydrate in lab was mixed with kaoline to form core samples, so as to simulate the hydrate-bearing sedimentary layers in the seabed. Under conditions of different confining pressure, triaxial compressive tests were conducted on hydrate-bearing sediments with different volume content of kaoline. The results show that: (1) The failure strength of gas hydrate-bearing sediments increases with the confining pressure at a low-pressure stage. The strength tends to decline gently with further increases of confining pressure. (2) The modulus of elasticity E0 keeps unchanged under various confining pressures. But the secant modulus E50 presents a great dependency on the confining pressure. Secant modulus increases to a peak and then decreases with the increase of confining pressure; (3) The internal friction angles of gas hydrate-bearing sediments are not sensitive to the volume ratio of kaolin, but its cohesion depends on the volume ratio of kaolin. The sediment strength increases with the increase of kaoline content.