Select

null

2004, 23 (14): 0-0 doi:

[PDF] 130 KB (793)

[HTML]

+

Show Abstract

Select

PHYSICAL AND NUMERICAL SIMULATION OF WATER FLOODING EFFECT IN FRACTURED SANDSTONE OIL RESERVOIR

null

2004, 23 (14): 2313-2313 doi:

[PDF] 313 KB (1275)

[HTML]

+

Show Abstract

In order to study the fluid flow in fractured sandstone oil reservoir，rock slice model is employed in the physical simulation of the water-flooding procedures of 6 models with different fissure modalities. By analyzing the physical simulation results，some beneficial laws are obtained. Based on the characteristics of fractured sandstone reservoir，equivalent continuum model for simulating fluid flow is put forward. According to the continuum model，the oil and water flow in the 6 fissure models is studied by numerical simulation. The applicability of the equivalent continuum models for fluid flow simulation in fractured sandstone reservoir is verified by comparing the numerical simulation results with the physical simulation results.

Select

GENERALIZED MULTIPLE POROUS MEDIA SEEPAGE MODEL OF GROUNDWATER SYSTEM FOR FANGEZHUANG MINE

null

2004, 23 (14): 2319-2319 doi:

[PDF] 405 KB (1249)

[HTML]

+

Show Abstract

For fully representing the characteristics of fractured rock masses，such as strong nonhomogeneity and discontinuousness，the media are studied with generalized multiple porous media theory. Geological research and hydrogeologic tests show that，as main fractures and vertical passageway of aquifer，karstic collapse columns have hydrogeologic characteristics and calculation mode of seepage rate different from that of joints in rock masses and should be generalized as another kind of main fractures. So，the groundwater system of Fangezhuang mine is simulated accurately by generalized multiple porous media seepage model in which fault F0，Jingkou syncline axis，Tatuo syncline axis and No. 13 karstic collapse column are main fractures，sandstone of coal floor is the target aquifer，equivalent porous media are among main fractures，and groundwater flow is mainly controlled by main fractures and obeys cubic law，karstic collapse columns work as water pipelines，and the fractured rock masses are equivalent to porous media. The model well represents dimensional characteristics of fractured system of groundwater，especially for the strong runoff zone and local discontinuous seepage. Water volume of colliery is forecasted with the model，and the results show that storage capacity and permeability of normal fractured rock masses in sandstone aquifer are poor，and the mining water in mine is mainly from sandstone aquifer recharged by Ordovician limestone with vertical passageways or fractures. By analyzing seepage fields and taking dewatering volume of the colliery as input，the stimulation results show that the natural volume and the largest volume of groundwater on the third mining level are 0.167 m3/s and 0.25 m3s respectively，and the total natural volume and the largest total volume of groundwater of this mine are 0.333～0.417 m3/s and 0.5 m3/s respectively.

Select

APPLICATION OF MODIFIED STOCHASTIC WALK METHOD TO SOLUTE TRANSPORT SIMULATION

null

2004, 23 (14): 2326-2326 doi:

[PDF] 260 KB (931)

[HTML]

+

Show Abstract

Stochastic walk method is an effective method of modeling solute transport in fracture network. Traditional stochastic walk method locates new position of particle though given time step. However，it is difficult to define the size of time step. The size of time steps has an important effect on precision of simulation results. In this paper，traditional stochastic walk method is modified. In the condition of known spatial step，the analytical expression is developed between time and spatial steps. As a result，the size of time steps is expressed by spatial step automatically，which can avoid artificial factors in defining time step. At last，traditional stochastic walk method，analytical method and modified stochastic walk method are compared through a case study. Results show that solute transport in fracture network can be modeled efficiently based on modified stochastic walk method and that the modeling result is of relative high accuracy.

Select

RANDOM NON-HOMOGENEOUS THERMAL ELASTIC MECHANICS MODEL AND NUMERICAL TESTS ON THERMAL CRACKING
THRESHOLD OF ROCK

null

2004, 23 (14): 2331-2331 doi:

[PDF] 290 KB (1223)

[HTML]

+

Show Abstract

Considering different micro-structure of rock，random non-homogeneous thermal elastic mechanics model and FEM based on this model are put forward. Numerical stimulation in made for plane stress state to study the influence of thermal dilatability on thermal cracking law and temperature threshold，and only thermal dilatability is considered as random variable and thermal dilatability is of uniform distribution，Gauss distribution and Weibull distribution. Stimulations show that relationship between temperature threshold and thermal dilatability of uniform distribution is a line function，relationship between temperature threshold and thermal dilatability of Gauss distribution is a power function，and relationship between temperature threshold and thermal dilatability of Weibull distribution is a power function.

Select

BP NETWORK UPGRADE STRATEGY AND SELF-ADAPTIVE UPGRADABLE PREDICTION MODEL OF TERRANE CRACK
DEPTH FOR COMBINED PERFORATING-FRACTURING

null

2004, 23 (14): 2336-2336 doi:

[PDF] 181 KB (987)

[HTML]

+

Show Abstract

There is a very expansive application foreground for prediction model of terrane crack depth for combined perforating-fracturing in oil well. Simple prediction model is very easy to achieve by ANN method with BP algorithm. However，the prediction credibility keeps unknown in condition that learning samples change after learning. So how to deal with the changing becomes an important issue. Much effort is made to approach a dynamic model that can adjust itself when samples partially change. Based on the investigation of ANN model with BP algorithm，an abecedarian upgrade strategy and algorithm of single hidden-layer BP networks are given in this paper. This strategy includes three key parts，classified learning with the basis of sample unit comparability judgment after sample space changes，self-adaptive arithmetic of classified sample appearance probability during learning and self-adaptive control method of network scale. Firstly，learning samples changes partially，and new samples will be sorted by the different aims of upgrade. Secondly，the upgrade learning starts from current state of the network，and network scale might be adjusted to suit the new sample space. Finally，with less upgrade learning steps，the network can adapt to the new sample space，without a whole second learning course. In order to test this strategy，the upgradeable self-adaptive prediction model of terrane crack depth for combined perforating-fracturing is established with the satisfaction of precision. All samples come from systemic numerical FEM analysis with FINAL under the condition of blast load. This model can adjust its scale and the weight matrix rapidly on the self-adaptive rule，in allusion to the local alteration of sample space. To the problem of sample changing in the ANN model，all of these practically offer a new way with single-hidden-layer BP algorithm. This self-adaptive upgrade strategy can be applied to other modeling courses.

Select

COMPLEXITY STUDY OF REDESTROYED STRATA CAUSED
BY DEEP MINING IN RESOURCE DEPLETION AREA

null

2004, 23 (14): 2341-2341 doi:

[PDF] 321 KB (1041)

[HTML]

+

Show Abstract

In the resource depletion area，there are many abandoned stopes and the strata have been destroyed many times after years of mining in top strata. The rules of further destruction caused by deep mining or simultaneous mining at the top and deep strata，and subsidence along depth direction and the accumulative effect of damage are analyzed. The complexity of strata redestruction and the mechanism of worsening of earthquake- resistant behavior in the resource depletion area are discussed，and evaluation methods and resuming measures of earthquake-resistant behavior are proposed.

Select

FRACTURE TOUGHNESS IN HYDRAULIC
FRACTURE PROPAGATION

null

2004, 23 (14): 2346-2346 doi:

[PDF] 255 KB (1771)

[HTML]

+

Show Abstract

Based on fracture mechanics and plastic mechanics，the plastic area at fracture tip in hydraulic fracture propagation is studied. The dimension of plastic area around the fracture is also quantitatively analyzed. The effect of fracture toughness in plastic area on the fracture dimension is discussed，and some relative parameters are obtained.

Select

STUDY ON INTERFERENCE AMONG HORIZONTAL MULTI-FRACTURES

null

2004, 23 (14): 2351-2351 doi:

[PDF] 325 KB (1184)

[HTML]

+

Show Abstract

The mechanism of the interference among horizontal multi-fractures is obtained by FEM analysis software (ANSYS) in the study of hydraulic fracturing in the thin and poor formations in the reservoirs. The larger the spacing of fractures is，the bigger the interference among them is. The bigger the number of layers being fractured is，the bigger the interference among them is. The mechanism can be applied to optimize the design of hydraulic fracturing and provide a theory reference for the alteration of thin and poor formations.

Select

NEW METHOD FOR MEASUREMENT OF IN-SITU
STRESSES AT GREAT DEPTH

null

2004, 23 (14): 2355-2355 doi:

[PDF] 195 KB (1318)

[HTML]

+

Show Abstract

A new method is presented for measurement of in-situ stresses at great depth，which is based on the experimental research on anisotropy of acoustic velocity and Kaiser effect of acoustic emission for deep formation cores. The different magnitude of acoustic velocity around the surface of core cylinder is caused by the different degree of unloading on the core. The magnitude of acoustic velocity is the minimum in the direction of maximum in-situ stress，and the maximum in the direction of minimum stress. Based on this principle，the relative position of the maximum and minimum horizontal principal in-situ stresses can be determined. Then the acoustic emission experiments are performed on the two core samples drilled from the certain position，and the horizontal in-situ stress state is determined. The advantage of this method is that the experiment can be performed on thin layer core instead of an integral core of 15 cm long without any fracture，and can improve measurement of in-situ stresses at great depth.

Select

REVIEW OF STUDY ON ROCK MECHANICS AT GREAT DEPTH AND ITS APPLICATIONS TO PETROLEUM ENGINEERING OF CHINA

null

2004, 23 (14): 2355-2355 doi:

[PDF] 311 KB (1078)

[HTML]

+

Show Abstract

The scopes and characteristics of rock mechanics at great depth are discussed. This paper introduces the full-scale drilling system，the measurement of geo-stresses，rock fracture toughness，static and dynamic rock parameters，the advances in techniques of well-bore stability prediction and measurement during drilling，and physical and numerical simulations of hydraulic fracturing，in China. The challenges facing rock mechanics at great depth and technical issues to be solved are presented.

Select

TESTING STUDY ON MECHANICAL PROPERTIES OF
POST-HIGH-TEMPERATURE GRANITE

null

2004, 23 (14): 2359-2359 doi:

[PDF] 268 KB (1484)

[HTML]

+

Show Abstract

Testing study is made on the mechanical properties of granite after undergoing different high temperatures. The mechanical properties include stress-strain curve，peak stress，peak strain，modulus of elasticity and Poisson’s ratio of granite. The results show that the temperature does not obviously affect the mechanical properties of granite in the temperature ranging from room temperature to 400 ℃. But the mechanical properties deteriorate rapidly with the increase of temperature when the temperature is above 400 ℃. In this case，the peak stress or the strength and modulus of elasticity decrease rapidly，the peak strain increases rapidly，and the Poisson’s ratio presents a tendency of decreasing as the temperature increases.

Select

TESTING STUDY ON PHYSICAL AND MECHANICAL PROPERTIES OF HEATED SALT ROCK WITHIN 240℃

null

2004, 23 (14): 2365-2365 doi:

[PDF] 205 KB (1137)

[HTML]

+

Show Abstract

Salt rock is regarded as the ideal host rock for nuclear waste disposal due to its advantageous geological conditions and physico-mechanical properties. Study shows that nuclear wastes still have strong radiation energy，and make the surrounding rock heavily heated after many years of underground disposal. So the study of the physical and mechanical properties of heated salt rock is important and essential to ensure the safety of nuclear wastes disposed in salt rock. Through a series of tests for heated salt rock at different temperatures ranging from 20 ℃ to 240 ℃ in this paper，several conclusions are generated as follows. (1) The ultrasonic velocity of salt rock decreases with the rising of temperature，and the the ultrasonic velocity and the temperature are of exponential relation. (2) Both the uniaxial compressive strength and the axial strains of salt rock increase with the rising of temperature，while the modulus of deformation turns to the opposite direction. (3) The characteristic of plastic deformation and strain softening becomes distinct at high temperatures，and through regressive analysis，a relation between the uniaxial compressive strength and the temperature is obtained. (4) The values of the cohesion and the internal friction angle of salt rock increase with the rising of temperature，and the strength equations of salt rock at 20 ℃，60 ℃，and 120 ℃ are obtained. (5) The peak shear strength and the ultimate friction strength of salt rock both increase with the rising of temperature，and the relation of shear strength and the temperature is obtained.

Select

VISCOELASTIC ANALYSIS OF WELLBORE SHRINKAGE
IN SALT FORMATION

null

2004, 23 (14): 2370-2370 doi:

[PDF] 190 KB (1366)

[HTML]

+

Show Abstract

In drilling engineering，drill pipe often sticks in salt formation because of wellbore shrinkage. In the past，salt formation is often regarded as an elastic or elastic-plastic body，and the effect of time is not taken into account. However，engineering practice shows that the deformation of deep salt rock increases with time，that is，salt formation is of viscoelasticity. Supposing that salt formation is an isotropic and homogeneous viscoelastic body which obeys the Maxwell model，the wellbore shrinkage is studied carefully，and an expression for predicting wellbore shrinkage is proposed according to the elasticity-viscoelasticity correspondence principle. The expression will provide important reference to solving the problems of wellbore stability and the sticking of drill pipe in salt formation.

Select

ANALYSIS ON MECHANICAL BEHAVIOR OF SALT
ROCK WITH BARE HOLE

null

2004, 23 (14): 2374-2374 doi:

[PDF] 221 KB (1023)

[HTML]

+

Show Abstract

The creep of salt rock is very harmful in petroleum drilling. The creep of salt rock is calculated and analyzed by finite element method. The relations among shrinkage of bare hole radii，creeping shrinkage time，hole depth，density of drilling fluid，in-situ stresses coefficient，non-uniform coefficient and time are given. The calculation results are successfully applied into Tarim oil field.

Select

SIMULATION ON CREEP OF SALT FORMATIONS
BY VOLUME-CONTROL METHOD

null

2004, 23 (14): 2377-2377 doi:

[PDF] 388 KB (853)

[HTML]

+

Show Abstract

The depth of salt formations in Zhongyuan Oilfield is 50～200 m. The salt formations will generate a non-uniform external squeeze stress during their creep deformation and the casing pipes may be damaged. Volume-control method is employed in the 3D numerical simulation of actual formation condition. Creep velocity，displacement and the distribution of horizontal squeeze stress on the casing pipe are obtained. The results are useful for adjustment of drilling parameters，design of casing string and prevention of casing damage.

Select

STUDY ON CASING LOADS IN CREEP FORMATIONS

null

2004, 23 (14): 2381-2381 doi:

[PDF] 226 KB (1047)

[HTML]

+

Show Abstract

The distributions of casing load with uniform and non-uniform in-situ stresses in creep formations are studied by analytical and numerical methods，respectively. Firstly，taking the casing as the elastic foundation, analytical method is employed to analyze the casing loads with uniform in-situ stresses in the creep formations. Secondly，due to the difficulty of the analytical method in treating non-uniform in-situ stresses，finite element method is used instead. It is found that，under the conditions of both uniform and non-uniform in-situ stresses，the casing load will approach the elastic solution with sufficient time duration. Furthermore，the conclusions from numerical simulation for the non-uniform in-situ stresses are just opposite to the present acknowledged ones. For example，the casing loads are determined not only by the stress difference，but also by the stiffness ratio. These new conclusions are very important for applications and laboratory experiments and need special attentions.

Select

THREE-DIMENSIONAL ELASTOPLASTIC FEM ANALYSIS ON BOREHOLE STABILITY

null

2004, 23 (14): 2385-2385 doi:

[PDF] 341 KB (1136)

[HTML]

+

Show Abstract

Most of the existing models for borehole wall stress are based on plane strain hypothesis. So some errors may be generated as compared with the real stress state of rock. Based on the theory of spatial coordinate transformation system，a new three-dimensional FEM model is for ERD borehole stability analysis. It converts the variation of deviation and azimuth of ERD to the variation of in-stiu stress components. So the model is stable for any wellbore trajectory. With the new three-dimensional FEM model，some research is done on the ERD wellbore stability under elastic and elastoplastic conditions. The results show that the elastoplastic formations can assimilate more energy through plastic deformation than the elastic ones. So the former will be more stable than the latter under the same exterior load. Case studies indicate that the lower-than-normal mud weight can be used for drilling the deep elastoplastic formation，which can not only keep the wall stability，but decrease the damage to formation.

Select

NUMERICAL SIMULATION ON EFFECT OF PRESSURE RELIEF OF WATER INJECTION WELL ON CASING SQUEEZE PRESSURE

null

2004, 23 (14): 2390-2390 doi:

[PDF] 295 KB (971)

[HTML]

+

Show Abstract

Casing damage during blowout of water injection well is common in many oil fields of China. In order to study the mechanism of the casing damage，fluid-solid coupling models for simulating casing stress and deformation are established，and the numerical simulation based on the finite element method is also given. By numerical simulation，the effects of relief discharge，geo-stress，fluid pressure difference，permeability，stratum thickness on casing extrusion pressure are studied. The simulation results show that，at the same relief discharge，the bigger the permeability is，the bigger the extrusion pressure of casing damage is. In the same geological condition，the smaller the oil reservoir thickness is，the bigger the extrusion pressure is. The simulation results are very helpful to the casing protection in oil fields.

Select

RESEARCH ON FLOOR HEAVE OF ROADWAY IN DEEP MINING

null

2004, 23 (14): 2396-2396 doi:

[PDF] 494 KB (1304)

[HTML]

+

Show Abstract

The deformation control of surrounding rocks is one of the key problems in deep mining. Only when the mechanism and control mechods of floor heave are correctly understood，the difficult problems in the support of roadways in soft rocks of deep mines can be solved. Based on the field investigation，model tests and numerical simulation，the features and mechanism of four kinds of floor heave of roadway in deep coal mining are discussed，the major factors affecting the floor heave are analyzed，and recent advance of control methods of floor heave in coal mines，including two cases in China，is summarized

Select

BURST-PRONE EXPERIMENTS OF COAL-ROCK COMBINATION AT
－1 100 m LEVEL IN SUNCUN COAL MINE

null

2004, 23 (14): 2402-2402 doi:

[PDF] 376 KB (1099)

[HTML]

+

Show Abstract

Rockbursts are violent failures in the ground，which break rock and expell it into excavation. Rockbursts have caused numerous casualty accidents and damages of underground workings，so the control of rockbursts is one major problem for deep underground mining from the both aspects of safety and economy. The Suncun Coal Mine is one of the deepest underground coal mines in China. The burst-prone experiments of coal-rock combinations at －1 100 m level (buried depth 1 310 m) in Suncun Coal Mine were made in lab. In order to investigate the rock burst-prone of deep coal seams of different thickness，7 groups of coal-rock combination samples with different height ratio were tested to study their mechanic properties and dynamic failure behaviors. The validity of research proposal is confirmed by application cases and the coal-rock burst-prone identification results for surrounding rocks at －1 100 m level are obtained. According to the experimental results of strength change of the coal-rock samples before and after water immersion，the countermeasures for rockbursts in ultra-deep coal mining conditions are proposed. More than 300 coal-rock samples were prepared for the burst-prone experiments. The tests show that the burst-prone tendency will potentially increase with the increase of height ratio of roof rock to coal.

Select

OBSERVATION OF FLOOD FRONT AND STRESS
STATE AROUND WELL

null

2004, 23 (14): 2409-2409 doi:

[PDF] 615 KB (878)

[HTML]

+

Show Abstract

The technology of real-time microseism monitoring in the operation-involved area of oil field is an interesting research topic. Some feasible standards and methods about discerning microseism signals are put forward and reliable observation results are obtained in several cases around the world. The observation systems and softwares are developed independently in this research according to the international experience，methods and standards，and satisfactory results are obtained with this methodology in the practices in Daqing，Huabei and Zhongyuan oil fields，China. With microseism observation of flood front at well J430 in fault block J11 of Huabei oil field as an example，the theory and method of observation and discernment criterion are introduced，and the feasibility of this methodology to obtain information about stress state and tectonics at great depth is proved.

Select

NUMERICAL SIMULATION ON FRACTURED ZONE OF ROADWAY IN HIGH STRESS AREA BY 3DEC AND ITS GPR VERIFICATION IN SITE

null

2004, 23 (14): 2413-2413 doi:

[PDF] 394 KB (1226)

[HTML]

+

Show Abstract

Developing features of fractured zones of roadway in isolated coal pillar area are theoretically studied by three dimensional distinct element code(3DEC). It is found in this paper that fractured zones of rock masses in high stress area are larger than those of others，but their horizontal displacement does not increase obviously. Small coal pillar in high stress area has pre-developed splits and large horizontal displacement，and its stress concentration degree is lower. For application in site，ground penetrating radar (GPR) is an effective method to determine the fractured zone and can be used to verify the theoretic results of 3DEC，which is important to locate roadways in site. GPR probing in field agrees with the result of numerical model of 3DEC. Therefore，the combined results of both stimulation and site probing present the reasonable position of roadway，which is 5～8 m to adjoining pits in the presented case.

Select

ANALYSIS ON COLLAPSE PRESSURE IN BLOCK I
OF JUNGGAR BASIN

null

2004, 23 (14): 2417-2417 doi:

[PDF] 218 KB (1073)

[HTML]

+

Show Abstract

Block I in Junggar Basin is the most important block of the western new exploration area of SINOPEC. Commercial oil and gas have been found in the well Z1 and S1. In the drilling process，the collapse of wellbore wall is severe in the Cretaceous and Jurassic strata. On the base of core experiment，the basic parameters that influence the collapse are calculated，and mud density for the stability of wellbore wall is determined. All of these ensure the further exploration and developing of oil and gas in future.

Select

COLLAPSE PRESSURE AND PRECAUTIONS
FOR STABILITY OF WELLBORE WALL

null

2004, 23 (14): 2421-2421 doi:

[PDF] 156 KB (1604)

[HTML]

+

Show Abstract

Instability of wellbore wall is a costly and troublesome problem in drilling operation. The stress formula of wellbore wall is given in this paper according to solid mechanics，and swelling stress properties of shale are also determined by swelling stress test on shale. Safe drilling mud densities are calculated by using Mohr-Coulomb strength criterion. The presented method has been employed in some field with good result.

Select

DETERMINATION OF ROCK MECHANICS PARAMETERS BY PRESSURE OF SURFACE FRACTURING TREATMENT

null

2004, 23 (14): 2424-2424 doi:

[PDF] 310 KB (1899)

[HTML]

+

Show Abstract

The rock mechanics parameters，such as Yang¢s modulus and Poisson's ratio，are determined on the basis of surface fracturing treatment pressure and instantaneous shut-in pressure during PAD stage. The first step is to calculate hole bottom pressure. Then the fracture propagation model is determined based on the curve of hole bottom pressure. In order to simplify the problem，PKN model and KGD model are utilized，and different equations are deduced for different fracture models. In essences，the relation curve of Yang¢s modulus and surface treatment pressure is determined based on the fact that the fracture width is not only related to Yang¢s modulus but also to net pressure within a fracture. The Poisson's ratio curve is also calculated out based on the curve of minimal horizontal stress which may be obtained by other reliable methods. Verified by another reliable technique，the presented new method is reliable and simplified and can be put into field applications conveniently. It can also be used to perform real time analysis as well as post-fracturing analysis.

Select

PREDICTION OF SAFE MUD DENSITY WINDOW BY INTERVAL VELOCITY BEFORE DRILLING

null

2004, 23 (14): 2430-2430 doi:

[PDF] 593 KB (1019)

[HTML]

+

Show Abstract

The propagation velocity of seismic wave is dependent on the property of formations，such as formation component，elasticity，density，depth，geologic age，porosity and tectonic activity. The distribution of interval velocity is rich in the information of the formations through which the seismic wave transmits，and can reflect the mechanic property of the formations. According to the interval velocity of the well，the adjacent structure of maximum correlativity is determined by correlation analysis. The interval velocity error compensation function is acquired by Fourier trend surface analysis according to the logged data of the wells in the adjacent structure. Based on the result of borehole stability for the adjacent structure，the prediction models of borehole stability before drilling are established according to trend surface analysis theory，then the safe mud weight range for TalimuYN4 well is determined accordingly before drilling. The field application testifies that the model is feasible.

Select

TESTING STUDY ON ACOUSTOELECTRIC
EFFECT IN MODEL BOREHOLE

null

2004, 23 (14): 2434-2434 doi:

[PDF] 257 KB (1023)

[HTML]

+

Show Abstract

The acoustoelectric effect of rock is investigated with experimental method in model borehole. Acoustic wave and electromagnetic wave are recorded in the condition of different salinity and the characteristics of the electromagnetic wave are analyzed by comparison with acoustic wave. The study results show that the converted electromagnetic wave is induced by the acoustic wave that propagates along the borehole，and the source of the acoustoelectric conversion is Rayleigh wave in the borehole. The electromagnetic wave radiated by the acoustic source is evidently different from the converted electromagnetic wave in frequency and phase. The water salinity is a main factor influencing the amplitude of the converted electromagnetic wave.

Select

TESTING STUDY ON ROCK DRILLABILITY EVALUATION
BY ACOUSTIC VELOCITY OF CUTTING

null

2004, 23 (14): 2439-2439 doi:

[PDF] 221 KB (1117)

[HTML]

+

Show Abstract

The rock drillability is an important index for optimizing the selection of drill bit. A new methodology for evaluating rock drillability by acoustic velocity of cutting is developed，which can easily and continuously provide drillability information of stratum. The feasibility of the measurement on rough rock fragments of very small dimensions and the correlativity between acoustic velocity of cutting and rock drillability index are investigated. The results show that the acoustic velocity obtained from small cuttings is well related to rock drillability index. The relation model between the index and the acoustic velocity is developed. Test drilling is performed and shows that this method is effective.

Select

TEST AND APPLICATION OF SONIC PROPERTIES
OF CARBONATE ROCK

null

2004, 23 (14): 2444-2444 doi:

[PDF] 172 KB (1199)

[HTML]

+

Show Abstract

Based on formation rock samples selected and collected from Northeast Sichuan area and buried-hill structure in Jiyang Depression and corresponding downhole acoustic logging data of the samples，the rock drillability and acoustic characteristics of the roller cone bit and the PDC bit are tested. Correlation of the compressive wave velocity and shear wave velocity of rock surface with drillability of roller cone bit and drillability of PDC bit respectively，and correlation between the compressive wave velocity of rock surface and the downhole-logged compressive wave velocity of the same formation rock samples are studied by means of mathematical statistics. A mathematical model is established for predicting drillability of carbonate formation profile by using acoustic logging data with coincidence rate F＞0.75. By substituting in-site acoustic logging data into the prediction model for calculations，the prediction accuracy is up to 91.7%，reaching and exceeding the expected technical target.

Select

ROCK MECHANICS PROBLEMS IN HORIZONTAL
WELL FRACTURING

null

2004, 23 (14): 2463-2463 doi:

[PDF] 225 KB (3624)

[HTML]

+

Show Abstract

Horizontal well is a new drilling technique developed in recent years，which can effectively reduce the cost of reservoir development. But some horizontal wells does not gain the perfect productivity，due to low permeability or some other reasons. The fracturing of horizontal well is an important technique to solve this problem. This paper studies the unique rock mechanics properties of horizontal well fracturing，especially the relation among in-situ stress magnitude，direction and fracture orientation.

Select

MODEL AND ELASTICITY ANALYSIS OF COLLAPSE STRENGTH
OF CASING-CEMENT MANTLE

null

2004, 23 (14): 2467-2467 doi:

[PDF] 155 KB (1503)

[HTML]

+

Show Abstract

A model is established for evaluating the collapse strength of casing-cement mantle of oil field subjected to external pressure and a concept of elasticity of collapse strength of casing-cement mantle is put forward. Based on this concept，the effect of cement mantle on the collapse strength of casing and the sensitivity of collapse strength to the parameter variation of cement mantle are calculated and analyzed.

Select

MULTIVARIABLE REGRESSION ANALYSIS OF TRIAXIAL COMPRESSION STRENGTH OF ROCK IN SHENGTUO OIL FIELD

null

2004, 23 (14): 2471-2471 doi:

[PDF] 185 KB (994)

[HTML]

+

Show Abstract

In order to deal with serious sanding problem in Shengtuo Oil Field in high water cut period，triaxial tests on the reservoir sandstone are carried out，and reliable data are gained. A few data closely related to the triaxial compression strength of the rock are selected as regression variables after well measurement data and core test data are analyzed and compared. The regression relation of compressive strength to well depth，rock density，porosity，interval transit time and Young¢s modulus of the reservoir rock is established in the process of introducing new important variables，checking the old variables and eliminating the unimportant variables continually. The regression relation can be used to calculate the compressive strength of reservoir rock in site and guide the sand control or fracturing projects.

Select

NEAR-WELLBORE EFFECTS IN HYDRAULIC FRACTURING

null

2004, 23 (14): 2476-2476 doi:

[PDF] 178 KB (1434)

[HTML]

+

Show Abstract

In hydraulic fracturing，there are always some puzzling phenomenon such as premature sand-out and abnormally high treatment pressure. In recent research of hydraulic fracturing，experimental and numerical simulations are performed on the effect of stress and perforation on fracture propagation at near-wellbore region. The results show that hydraulic fracture propagation is not only related to the orientation of borehole in the stress field，but the magnitude of principal stresses. In addition，these research results provide some suggestions on diagnosing potential fracture reorientation and eliminating the effect during hydraulic fracturing treatment.

Select

ORIENTATION DETERMINATION OF MAXIMUM HORIZONTAL
STRESS IN RESERVOIR FORMATION BY PALEOMAGNETIC ORIENTATION OF CORES

null

2004, 23 (14): 2480-2480 doi:

[PDF] 251 KB (1293)

[HTML]

+

Show Abstract

In exploration and production of oil and gas reservoir，the determination of in-situ stress orientation is essential for the distribution of natural fracture，arrangement of water flooding wells，design of horizontal well and water fracturing，optimal program of water injection and oil development adjustment. The paleomagnetic method for the determination of maximum horizontal stress orientation is introduced. The original orientation of the core in the reservoir formation can be obtained by paleomagnetic orientation of cores，and the relative orientation of maximum horizontal stress to the datum line in cores can be obtained by using the Kaiser effect of acoustic emission of rocks. Combining paleomagnetic orientation of cores with Kaiser effect of acoustic emission，the original orientations of the maximum horizontal stresses in the reservoir formation are then obtained. The results by the presented method are fundamentally consistent with diplog in a case in Jing’an oil field.

Select

STUDY ON PREDICTION OF FRACTURING PRESSURE
OF SHALLOW LAYER

null

2004, 23 (14): 2484-2484 doi:

[PDF] 165 KB (966)

[HTML]

+

Show Abstract

The formation fracturing pressure is important for determining the safe mud density，designing the well profile and predicting the initial fracturing of hydraulic fracture. The fracturing pressure is dependent on in-situ stress，well deviation and the anisotropy of tensile strength. The in-situ stress and rock mechanics parameters are studied，the stress distribution around wellbore is analyzed，and the prediction model of fracturing pressure is established，which is successful in field application.

Select

STUDY ON NEW NON-DARCY PATTERN OF OIL FLOW IN POROUS MEDIA AND ITS APPLICATION

null

2004, 23 (14): 2488-2488 doi:

[PDF] 97 KB (1008)

[HTML]

+

Show Abstract