钻井液与完井液

Abstract:
The methods of preventing and curing gas hydrate in deepwater drilling are too preservative. In the west of the South China Sea, the gas hydrate inhibitive drilling fluid HEM used in the deepwater drilling is quite expensive and the penetration rate is low. To reduce the mud cost and shorten the drilling time, several issues were studied, including the phase equilibrium curves of hydrate generation with different gas components, the regions for gas hydrate generation under different operating conditions, and the methods of dealing with borehole blockage by the gas hydrates. All these studies were conducted with the low cost polymer drilling fluids used in the deepwater drilling in the BD block in the Yinggehai basin (South China Sea). Potential regions for the generation of gas hydrates under different operating conditions were obtained. Based on these studies, poly (M-vinyl caprolactam) was selected as the kinetic gas hydrate inhibitor to inhibit the generation of gas hydrates glycol selected as the thermodynamic inhibitor to remove blockage in a wellbore by gas hydrates. Ten new kinetic inhibitors were designed in laboratory study, of which the DS-A3 inhibitor has good inhibitive capacity for gas hydrate generation. Laboratory study and field (block BD) application showed that: 1) in operating conditions such as normal drilling, circulation and well shut-in, no gas hydrate generation region exists, as such, there is no risks of wellbore blockage. 2) Considering the inhibitive effect and cost together, 0.8% poly (M-vinyl caprolactam) has the best inhibitive effect for gas hydrate generation, and 45% glycol has the best effect for removing blockage of a wellbore by gas hydrate. 3) When there are no complex downhole operating conditions, if the rig down time does not exceed 15 hours, polymer drilling fluids can be directly used in deepwater drilling. In this way the drilling fluid cost for a single well can be reduced by 50%-70%, a good economic benefit.

Prediction of Four Kinds of Sensibility Damages to Hydrocarbon Reservoirs Based on Random Forest Algorithm

SHENG Keming, JIANG Guancheng

2023, 40(4): 423-430. doi: 10.12358/j.issn.1001-5620.2023.04.002

Abstract(453) HTML (186) PDF (3412KB)(106)

Abstract:
Many kinds of hydrocarbon reservoir damages with complex mechanisms have been encountered in every phase of oil and gas field exploration and development. Conventional core flow test used in evaluating the sensibility damage of a reservoir can give reliable test results, however, this test is both expensive (coring, for instance) and time consuming. Researches have shown that a model established with neural network and random forest algorithm on small-scale samples can be used to save time and money in predicting the properties of samples. In this study, the data of a set of small-scale samples tested in laboratory is obtained from the block X. The training-sets and testing-sets are then selected on the samples. By extensively comparing the results of three algorithms, which are the BP neural network algorithm, the radial basis function neural network algorithm and the random forest algorithm, the random forest algorithm is finally selected as the main method of quantitatively diagnosing the sensitivity damage of hydrocarbon reservoirs. To improve the prediction accuracy, algorithms such as grid search are used in hyperparameter optimization, and data dimensionality reduction is performed based on factor weight. A complete model is finally established based on the studies conducted. The average R² value of the four kinds of reservoir damage model is 0.852, with a prediction accuracy between 90.00% and 95.68%.

Research and Application of Dual-protective Oilfield Water Drilling Fluids System Without Solid

LI Sheng

2023, 40(4): 431-437. doi: 10.12358/j.issn.1001-5620.2023.04.003

Abstract(519) HTML (197) PDF (2015KB)(114)

Abstract:
During the development of the carbonate reservoir of the Tahe oilfield, the conventional polysulfonate drilling fluid damages reservoir duo to non-acid-soluble solid phase after loss, and sulfonalized agent does not conform to the concept of green development. The oilfield water is introduced to formulate a solid free drilling fluid to avoid damage reservoir from solid, and the key treatment agents such as anti-high temperature anti-calcium viscosifier, flow pattern modifiers, high-temperature anti-calcium polymer filtrate reducer. The dual-protective oilfield water drilling fluids system without solid was developed. Indoor evaluation datas show that the drilling fluid was heat resistant to 150 ℃, the ratio between yield point and plastic viscosity is as high as 0.68～0.76 Pa/mPa·s, the EC₅₀ value of biological toxicity indicators is as high as 28,600 mg/L, and the bio-degradation index BOD₅/COD_Cr is as high as 21.35%. The dynamic permeability recovery value is as high as 91.8%, which has good formation damage control performance. The developed dual-protective oilfield water drilling fluids without solid were successfully used in more than ten sidetrack wells,and the application effect was significant.

Mechanisms of Borehole Instability of the Shaximiao Formation in Block Zhongjiang and the Anti-collapse Alkyl Glycoside Drilling Fluid

CHEN Wenke, ZHENG He, GONG Houping, XU Chuntian, CAI Wei, SHI Shuijian, ZHOU Chengyu, BAO Dan

2023, 40(4): 438-445. doi: 10.12358/j.issn.1001-5620.2023.04.004

Abstract(515) HTML (187) PDF (3949KB)(108)

Abstract:
Borehole wall instability has long been a problem encountered in drilling the Shaximiao formation in the block Zhongjiang, western Sichuan. To solve this problem, the claystones from the Shaximiao formation was studied for their mineral composition, microstructure and physical-chemical properties. The study results have revealed the mechanisms of borehole wall instability of the Shaximiao formation. The Shaximiao formation is a typical hard and brittle rock with high content of clay minerals (mostly illite) which are strongly hydratable. The formation is developed with plenty of micrometer- and nanometer-sized fractures, which will expand continually when mud filtrate invasion take place and finally, collapse. The inhomogeneous distribution of illite and illite/montmorillonite mixed layer in the rocks, high specific water absorptivity and high repulsive force of the hydration films have made the expansion of the microfractures even worse. An alkyl glycoside inhibitive agent and a nanometer plugging agent were selected to formulate a high-performance anti-collapse drilling fluid based on the “Multivariate collaboration” borehole stabilization theory. Laboratory experiment on the performance of this drilling fluid has shown that this drilling fluid has good rheology, API filter loss of less than 3 mL, HTHP filter loss of 8 mL or less, percent cuttings recovery of 98.87%, swelling rate of less than 3%. These data indicate that the drilling fluid has good inhibitive capacity and good capacity of plugging the microfractures and micropores. Field application has shown that the alkyl glycoside drilling fluid can effectively inhibit the collapse of the Shaximiao formation. High ROP was obtained with this drilling fluid, and no downhole troubles have been encountered. The use of the alkyl glycoside drilling fluid has provided a technical support to safely, efficiently and economically drill the Shaximiao formation.

Study and Application of an Oil-based Gel Fluid for Sealing Induced Micro-fractures

LI Wenzhe, FU Zhi, ZHANG Zhen, LIU Yingmin, WU Shuang

2023, 40(4): 446-452, 461. doi: 10.12358/j.issn.1001-5620.2023.04.005

Abstract(420) HTML (164) PDF (3211KB)(100)

Abstract:
The Longmaxi formation in the Changning block (Sichuan Oilfield) is drilled with oil-based drilling fluids. This formation is developed with microfractures and hence mud losses have frequently happened in the past. Mud losses have been controlled with bridging particles formulated in oil-based slurries, which has been proved unsuccessful and time consuming. To deal with this problem, a compound oil-based gel has been developed with animal fats, vegetable oils and epoxy resin. This oil-based gel can invade into the fractures in the formation rocks to seal them off, thereby increasing the success rate of mud loss control. Considering the practicability of field application, the compressive strength, thickening time and performance against contamination from oil-based muds of this gel were evaluated in laboratory test, and its ability to combat mud losses was also evaluated. The laboratory test results have shown that the gel has compressive strength of 5.1 MPa, and the gelling time can be controlled at more than 3 hours, which is enough to perform field operation safely. Oil-based drilling fluids have only a very slight effect on the gel strength of the gel and do not cause the thickening time of the gel to shorten. All properties of the oil-based gel indicate that it is suitable for use in controlling mud losses through microfractures in hole sections drilled with oil-based drilling fluids.

Development of Ultra-high Temperature Polymer Brush Lubricant for Water Based Drilling Fluids

GAO Chongyang, HUANG Xianbin, BAI Yingrui, SUN Jinsheng, LYU Kaihe, ZHANG Yu, ZONG Jiajiang, LIU Fengbao

2023, 40(4): 453-461. doi: 10.12358/j.issn.1001-5620.2023.04.006

Abstract(510) HTML (187) PDF (2624KB)(116)

Abstract:
During oil and gas drilling in deep complex formations, the technical requirements of high temperature and salt-resistance of drilling fluid should be met. In this paper, a polymer brush lubricant (HLM) for water-based drilling fluids was prepared using methyl methacrylate, lauryl acrylate and 2-hydroxyethyl acrylate as the main raw materials and 2-methylpropionitrile as the initiator. The HLM was characterized by means of Fourier infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermogravimetric analysis and gel chromatography. The compatibility of HLM with drilling fluids and the lubricity performance of HLM under high temperature, high salt and high density conditions were evaluated. The lubricity was further analyzed using a multifunctional material surface performance tester and a four-ball friction tester. The experimental results showed that HLM had a good thermal stability with a weight average molecular mass of 3494. HLM had good compatibility with the bentonite-based mud at room temperature and had essentially no effect on rheology. The temperature resistance can reach 260 ℃.When concentration of HLM was 2%, the lubrication coefficient reduction rates were 91.16% under room temperature, 88.24% after ageing at 260 ℃, 75.69% for the saturated salt-based mud, and larger than 40% in the high-density drilling mud. The multifunctional material surface performance experiment further demonstrated that HLM could substantially reduce metal-to-metal friction. The four-ball friction experiment demonstrated that HLM could form a stable lubricating film on metal surfaces. Since HLM had multiple adsorption sites and strong adsorption capacity, the adsorption film still had high strength under high temperature and high salt conditions, giving HLM good lubricating properties. This paper can provide technical reference for the construction of drilling fluids for deep/ultra-deep formations.

Study and Application of a Graphene Lugging Agent for Water Based Drilling Fluids

ZHANG Hongwei, HUANG Guoqiang, WU Hongling, YANG Yin, LU Changbo, CHENG Zhi

2023, 40(4): 462-466. doi: 10.12358/j.issn.1001-5620.2023.04.007

Abstract(500) HTML (185) PDF (3203KB)(109)

Abstract:
Fast plugging of microfractures and micropores in the hard brittle shales and deep buried sandstone/mudstone interbeds is one of the challenges that needs to be dealt with in solving borehole wall collapse in drilling the shale formation and reservoir damage. Graphene materials, because of their excellent properties such as nanometer sizes and layered membrane structures, can be used to solve these downhole problems at low concentrations and with high efficiency. A graphene slurry with good stability is prepared in laboratory with graphite using rolling lift-off technique. Evaluation of the performance of the graphene slurry shows that the D₅₀ of the graphene particles is ±5 μm. The graphene slurry has good filtration control property and shale swelling inhibitive capacity. PPA test results show that the graphene slurry is able to effectively seal off the micropores on the sand plate. The application of the graphene slurry on two wells shows that it has good compatibility with the water based drilling fluids used and improves the plugging efficiency of the drilling fluids. Using this graphene slurry, the borehole wall collapse problem previously encountered is successfully solved.

Reservoir Friendly Ultra-fine Manganese Tetroxide for Drilling Fluids

WANG Long, FANG Jing, DONG Xiumin, WANG Jinshu, FANG Junwei, GENG Yunpeng, ZHANG Jianjun, XU Tongtai

2023, 40(4): 467-474. doi: 10.12358/j.issn.1001-5620.2023.04.008

Abstract(523) HTML (177) PDF (3514KB)(84)

Abstract:
High density drilling fluids weighted with barite were used in deep well and ultra-deep well drilling in the Shunbei block. Several problems were found with these drilling fluids during drilling, such as difficulties in maintaining mud rheology, poor settling stability as well as reservoir damage by the solid particles from the drilling fluids etc. Micromax as a weight material has been reported in dealing with these problems, but the use of Micromax in China has been limited because of technical monopolization and high cost. A new drilling fluid micro-manganese weighting additive DFMT01 was developed using the “manganese ore method”. As a cost-effective domestic micro-manganese product, DFMT01 was used to formulate reservoir protective drilling fluids. The molecular structure of DFMT01 was characterized, and the performance of DFMT01 was evaluated in the high density sulfonated drilling fluids used in the Shunbei block. The results of field application of DFMT01 show that it has good physical and chemical properties. DFMT01 has a density of 4.7 g/cm³, an acid solubility of at least 99%, a D₅₀ of 1.17 μm and particle sphericity of 0.967, all these properties are comparable to the equivalent products from abroad. Drilling fluids weighted with DFMT01 have rheology, filtration property, erosion property and reservoir protective capacity equal to or better than those of the drilling fluids weighted with Micromax. A “neutralize to precipitate calcium carbonate – recover manganese ions with sulfuric acid – coagulate to treat the waste water” method was used in the treatment of high concentration acidic waste liquids containing manganese. Using this method, waste waters after treatment has mass concentration of manganese of 0.45 mg/L and SS of 10 mg/L, reaching the requirement of the first-level standard. The waste water treatment method can be used in the manufacturing, using and treatment of DFMT01 as a closed loop. DFMT01 is a weighting material having excellent property, low cost and very broad promotion and application prospects.

An Environmentally Friendly Non-foaming Anti-water Blocking Agent

CHU Qi

2023, 40(4): 475-480. doi: 10.12358/j.issn.1001-5620.2023.04.009

Abstract(435) HTML (162) PDF (2491KB)(80)

Abstract:
In order to improve the bubble inhibition and environmental protection performance of the waterproof locking agent for drilling fluid, a natural modified product SMFS-1 was synthesized from alginic acid, 2-(2-aminoethylamino)ethanol (AEEA), epichlorohydrin (ECH) and pentaerythritol (PETP) as raw materials. The molecular structure was characterized by Fourier infrared spectrometer (FT-IR). The test results of waterproof lock performance show that the surface tension of aqueous solution can be reduced to less than 25 mN/m after the addition of SMFS-1, which can reduce the volume of core self-absorption, promote the change of rock surface from hydrophilic to neutral, and increase the recovery value of core permeability to more than 80%. SMFS-1 is resistant to temperature up to 120 ℃, has excellent adsorption performance, no bubbling effect, and has little impact on rheological properties and filtration properties of drilling fluid. The environmental performance test results showed that the semi-lethal concentration (EC₅₀) of SMFS-1 was 32,250 mg/L, and the biodegradability evaluation index (Y) was 17.36, which met the emission standard and was easy to biodegrade.

Improving the Performance of Filter Loss Reducer Lignite Resin with Ultrasonic Induction

PENG Bo, GUO Wenyu, MU Weirong, LI Yufeng

2023, 40(4): 481-486. doi: 10.12358/j.issn.1001-5620.2023.04.010

Abstract(413) HTML (159) PDF (3255KB)(78)

Abstract:
A water based mud was formulated with lignite resin and bentonite in laboratory in accordance with the standard SY/T 5679—2017. After agitating the mud with high-speed mixer, the mud was treated with ultrasonic wave to investigate the effects of ultrasonic vibration on the colloidal properties of the mud. The purpose of this test is to find a new way of preparing mud with which the performance of the existing mud additives can be improved. The test results show that ultrasonic vibration can remarkably reduce the filtration rate of the water based mud formulated. In the test the filtration rate of the mud is continuously reduced at increased power of the ultrasonic wave and in the length of time the ultrasonic wave is working. Furthermore, the apparent viscosity of the mud is slightly reduced by the action of the ultrasonic wave. With an ultrasonic wave of 20 kHz/850 W acting on the mud for 14 min, the API and HTHP filtration rates of the water based mud are reduced by 26.7% and 27.6% (both maximum reductions) respectively. The thickness of the mud cakes is also reduced by 30%-35% after the action of the ultrasonic wave on the mud. Filtration test on a brine mud shows that the API and HTHP filtration rates are reduced by 29.5% and 32.7% (both maximum reductions) respectively after the action of the ultrasonic wave. Particle size distribution analysis, adsorption experiment and SEM observation show that ultrasonic wave is able to reduce the average size of the bentonite particles and increase the adsorptive capacity of the lignite resin on the particles of bentonite, thereby helping form a denser thin mud cake under the action of pressure differential of the mud. Laboratory studies show that mixing new mud with ultrasonic wave is beneficial to improving the filtration property of lignite resin water based drilling fluids. This performance of ultrasonic wave is the so-called “acoustic cavitation mechanisms”.

Development and Evaluation of a Hyperbranched Polymer for Temporary Plugging Coalbed Methane

HUANG Wanlong, LIU Hanyu, ZHAO Mingfang, WU Haixian

2023, 40(4): 487-494. doi: 10.12358/j.issn.1001-5620.2023.04.011

Abstract(309) HTML (120) PDF (2532KB)(50)

Abstract:
To solve the problem of reservoir damage in coalbed methane development, a hyperbranched polymer temporary plugging agent MTA was developed based on the theory of reservoir protection by temporary plugging. The synthesis of MTA involves the use of raw materials such as methyl methacrylate, methyl acrylic anhydride and tert-carboxyl betaine etc. The performance of MTA was evaluated in laboratory experiment. IR spectroscopy shows that the three monomers have successfully copolymerized to form a new polymer. The thermal decomposition temperature of MTA is 252 ℃. Physical-chemical performance analysis results show that MTA has a molecular weight of 6 × 10⁴, an amine number of 17.52, a pH of greater than 7.0 and an average particle size of 0.69-3.32 μm. Compared with the commonly used plugging agents, MTA has better ability in reducing pressure transmission. The capacity of MTA in inhibiting the swelling of clays is equivalent to the inhibitive capacity of polyamines; it reduces the interlayer space of a clay from 1.92 nm to 1.58 nm. Under the action of a differential pressure, MTA can plug the micropores in formation rocks to stop the invasion of water into the formation. Furthermore, MTA can be adsorbed onto the surfaces of a rock by the action of electric charges, thereby forming a layered structure to hinder the filtration of water molecules into the rock. Evaluation of MTA reveals that MTA has good compatibility with other additives in a working fluid, and reduces the amount of filtrate of the work fluid by 41.2%. At 150 ℃, MTA working fluid has excellent performance sustainability and contamination resistance; it is resistant to contamination by 10% NaCl, or 5% CaCl₂, or 10% clays of poor quality. Rock samples treated with the MTA fluid have their permeability recovered by 87.3%. In field operations, MTA showed excellent performance in maintaining borehole stability; the rate of hole washout was less than 5%.

CEMENTING FLUID

Comparative Study on Effects of Different Crystallographic Materials on Self-healing of Fractures in Set Cement under CCUS Well Work Conditions

RAO Zhihua, DENG Chenghui, MA Qianyun, WU Guang'ai, WU Zhiqiang, CHENG Xiaowei

2023, 40(4): 495-501. doi: 10.12358/j.issn.1001-5620.2023.04.012

Abstract(317) HTML (134) PDF (3451KB)(50)

Abstract:
To achieve the goal of carbon neutrality as soon as possible, carbon capture, utilization and storage (CCUS) is an indispensable technology. High temperature high pressure environment in CCUS operations causes large stress and temperature fluctuations which in turn result in fractures in cement sheaths. These fractures in cement sheaths are a threat to the safe sequestration of CO₂. To deal with this problem, calcium carbonate whisker and graphene oxide are used as crystallographic materials to induce carbonization crystallization on the surface of the fractures developed in set cement, and the effects of the crystallographic materials on the self-healing of the fractures in the set cement were studied. Experimental results show that after different periods of carbonization self-healing reaction, the compressive strengths of the set cement samples from cement slurries treated with calcium carbonate whisker and graphene oxide separately are all higher than the compressive strength of the blank set cement sample. μ-CT results show that the set cement samples containing calcium carbonate whisker and graphene oxide have percent self-healing of the volume of the fractures of 55.24% and 74.60%, respectively, higher than the percent self-healing of the volume of the fractures in the blank set cement sample, which is only 18.32%. Phase analyses of the substances at the surfaces of the fractures in the set cement samples show that as the time for the carbonization increases, the CaCO₃ crystal contents at the surfaces of the fractures of the set cement samples containing crystallographic materials are higher than that of the blank set cement sample. From the experiment results it can be seen that the calcium carbonate whisker and the graphene oxide can be used as crystallographic materials to improve the carbonization self-healing ability of the fractures in cement sheath under CCUS work conditions.

Study on Flushing Efficiency of Drilling Fluid Filter Cake in Oval Wellbore

TU Qiang, WANG Haiping, FU Jianglong, FAN Likun, LI Zhi, GUAN Hong, ZHANG Xingguo

2023, 40(4): 502-510. doi: 10.12358/j.issn.1001-5620.2023.04.013

Abstract(303) HTML (122) PDF (4547KB)(49)

Abstract:
At present, the research on the flushing efficiency of drilling fluid filter cake in cementing engineering mainly focuses on the flushing condition of the circular hole casing in the middle, while the research on the influence of the hole shape and casing eccentricity on the flushing efficiency of drilling fluid filter cake is less. This study uses the drilling fluid filter cake flushing simulation experimental device to test the influence of eccentricity and flushing flow rate in the elliptical hole on the drilling fluid filter cake flushing efficiency, and analyzes the flow field of the flushing fluid in the annulus based on the computational fluid dynamics (CFD) method, calculates the hydraulic shear force of the flushing fluid, and clarifies the mechanism of the change of the filter cake flushing efficiency. The results show that when the short axis direction in the annulus of the elliptical hole is eccentric, the flushing efficiency of the drilling fluid filter cake is the largest in the long axis direction of the annulus, followed by the wide and short axis direction, and the narrow and short axis direction is the smallest; By increasing the eccentricity of the short axis in the annulus, the flushing efficiency of the drilling fluid filter cake decreases slightly in the long axis direction, increases in the wide and short axis direction, and decreases significantly in the narrow and short axis direction; With the increase of annulus flushing flow, the overall flushing efficiency of annulus drilling fluid filter cake is significantly increased, but the increase of filter cake flushing efficiency in the long axis direction of the annulus is the largest, followed by the wide and short axis, and the narrow and short axis is the smallest.

Preparation and Evaluation of a Nanometer Emulsion Flushing Spacer

MENG Renzhou, MOU Shaomin, LI Yuan, WANG Chengwen, YU Yongjin, QI Fengzhong

2023, 40(4): 511-518. doi: 10.12358/j.issn.1001-5620.2023.04.014

Abstract(352) HTML (130) PDF (5409KB)(52)

Abstract:
Oil based drilling fluids have been widely used in drilling unconventional wells, and one of the key problems with the use of oil based drilling fluids is how to effectively clean off the residue mud and the mud cakes on the borehole wall to provide a good bonding surface for cement slurries. Nanometer emulsion has low surface tension, small droplets and strong solubilization capacity, making it a good flushing fluid for cleaning residue oil based drilling fluids. Take the flushing efficiency and the sizes of the emulsion droplets as the evaluation criteria, a nanometer emulsion was selected as a flushing fluid for residue oil based mud cleaning. By testing the stability, electric potential and sizes of the droplets, the compatibility of the emulsion and spacer additives was analyzed, and a nanometer emulsion flushing spacer was formulated as a result of the study. Laboratory studies show that by changing the ratio of two surfactants, which are alkyl glycoside and polyoxyethylene ether, from 2∶8 to 9∶1, the flushing efficiency of the nanometer emulsion first increased and then decreased, the sizes of the droplets first decreased and then increased. The consistency between the flushing efficiency and small droplet size of the nanometer emulsion provides a theoretical basis for selecting an emulsion with both high flushing efficiency and dynamic stability. Some polymer additives will increase the viscosity of the nanometer emulsion and the oil-water interfacial tension, but do not significantly affect the stability of the nanometer emulsion. Surfactants with opposite charges will decrease the Zeta potential of a nanometer emulsion droplet, leading to a decrease of the stability of the nanometer emulsion. Commonly additives can be directly used to control of properties of a nanometer emulsion and to make nanometer emulsion flushing spacers. The spacer formulated in this study has stable rheology, high settling stability and good compatibility with cement slurries at temperatures up to 100 ℃. At 120 ℃, the spacer has flushing efficiency in 3 min of more than 99% and is able to remarkably enhance the bonding strength of the cement sheaths on the walls of the borehole drilled with an oil based drilling fluid.

A New Technology for Evaluating Job Quality of Well Cementing Based on Ultrasonic Lamb Wave and Its Application

WANG Minghui, LI Jin, HAN Yaotu, LI Jiling, LIU Huixin

2023, 40(4): 519-526. doi: 10.12358/j.issn.1001-5620.2023.04.015

Abstract(373) HTML (141) PDF (4451KB)(45)

Abstract:
The conventional CBL/VDL sonic log, sector bond log and ultrasonic pulse echo log all are unable to be used to accurately evaluate the quality of well cementing with light-weight cement slurries. To deal with this problem and improve the accuracy of evaluating the quality of well cementing with light-weight cement slurries, an ultrasonic Lamb wave well logging instrument for cementing job quality evaluation was developed based on ultrasonic “pulse-echo” detection mechanism. A model was established describing the relationship among the bending Lamb wave attenuation rate, the vertical echo resonance efficiency and the sonic impedance of medium outside casing. A chart was developed to evaluate the solid-liquid-gas three phase media. With the model and the chart, a new method for evaluating the quality of well cementing based on ultrasonic Lamb wave was developed in connection with light-weight calibration well logs. This new method can be used to effectively evaluate the quality of well cementing with light-weight cement slurries and detect the height of the cement return, thus having solved the difficulties encountered with the light-weight slurries. This technology has provided a clue for examining and evaluating the quality of well cementing with light-weight cement slurries. Meanwhile, the ultrasonic Lamb wave well cementing job quality log instrument can also be used to evaluate the casing eccentricity and casing wear, the results of which can be used as a basis for evaluating the quality of well cementing and the integrity of the wellbore. This new technology will have a broad application prospect.

Study and Application of a Fly Ash-slag Bonding Reinforcement Material

QIN Zhongkui, DONG Zhiming, PU Jian, ZENG Yong, LAN Xiaolin

2023, 40(4): 527-534. doi: 10.12358/j.issn.1001-5620.2023.04.016

Abstract(365) HTML (133) PDF (3967KB)(51)

Abstract:
When using a low-density cement slurry to cement a well, several problems need to be addressed, such as low early strength, deviation in compatibility with cement and high operation cost. To solve these problems, studies were conducted on fly ash and slag for their chemical composition, specific surface area and micromorphology using XRF, XRD and SEM etc. The study results have shown that the particle sizes of the fly ash and slag are distributed mainly in ranges of 0.36 – 89.34 μm and 1.56 – 39.91 μm, respectively, the specific surface area of the fly ash and the slag is 0.822 m²/g and 1.79 m²/g, respectively. The particles of these two materials have smooth surfaces and are closely packed. By analyzing the working mechanisms of the reinforcement materials, some organic and inorganic reinforcement materials were selected, taking the compressive strength of the flay ash cement slurry as the primary technical indicator. The optimum ratios and concentrations of these materials in the final reinforcement material were determined through laboratory studies as follows: 35%KZ+8%FMH+ 8%WK+3%NY+2%NS+6%CS. An alkali-activated fly ash-slag compound bonding reinforcement material was developed. The reaction process, micro structure and compressive strength of the alkali-activated fly ash-slag compound bonding reinforcement material in the QZ and FMH cement slurries were studied. Evaluation of the general performance of the bonding reinforcement material showed that when the concentrations of the bonding e reinforcement material in these two cement slurries are 10% and 9% respectively, the property of the cement slurries is able to meet the requirements of field operations. The bonding reinforcement material has been used in 7 well/times and the well cementing quality was 100% certified, achieving the expected goals.

FRACTURING FLUID & ACIDIZING FLUID

Research and Application of High-efficiency Bactericide for Guar Gum Fracturing Fluid

CHANG Qing, ZOU Chunfeng, CAI Jingchao, WANG Yue, ZHANG Qiuhong, LI Fengguang, YANG Chao

2023, 40(4): 535-539. doi: 10.12358/j.issn.1001-5620.2023.04.017

Abstract(349) HTML (133) PDF (2344KB)(49)

Abstract:
In response to the problem of guar gum fracturing fluid being affected by bacteria and other microorganisms during the summer in Daqing area, which leads to deterioration, and hydration, and affects the success rate of construction, the microbial diversity sequencing technology was used to analyze the bacterial species of guar gum fracturing fluid in three reservoir tanks constructed at the same time in different blocks, and the Quaternary ammonium cation composite polylysine high-efficiency bactericide was developed. The bactericidal effect of the new compound bactericide on fracturing fluid in Daqing area was evaluated by plate counting method. The experimental results showed that the newly developed compound bactericide could make the sterilizing rate reach 100% in 2h. A total of 352 sections were applied in 8 wells on site, and the viscosity retention rate of guar gum fracturing fluid was still 90% after 72 hours. This bactericide effectively solves the technical problem of rapid deterioration of on-site guar gum fracturing fluids, providing important performance guarantee for smooth fracturing construction, and has important application prospects in plant gum fracturing fluids.

Effect of Natural Fracture on Reservoir Temperature Distribution during Fracturing

SHI Mingxing, LI Qin, QIU Siyang, LEI Yun, JING Wei

2023, 40(4): 540-550. doi: 10.12358/j.issn.1001-5620.2023.04.018

Abstract(310) HTML (124) PDF (4234KB)(49)

Abstract:
In hydraulic fracturing, the pre-fluid not only plays a role of fracture formation, but also plays an important role of cooling in high temperature reservoir, which affects the effect of hydraulic fracturing. In order to study the influence of natural fractures on the cooling process of precursors, the temperature field of hydraulic fracturing in fractured reservoirs was simulated based on the finite volume method, and the influence of natural fractures on the temperature field of fractures in the process of injection was analyzed. On this basis, the influence law of natural fractures parameters on the reservoir temperature distribution and the cooling efficiency of precursors was discussed. Simulation results show that: Other conditions being the same, the greater the density of natural fracture, the wider the fracture width, and the smaller the angle between the fracture and the artificial fracture, the greater the reduction in reservoir temperature during the transformation, the higher the efficiency of the pre-fluid cooling, and the less pre-fluid required to cool the reservoir to the same temperature, natural fracture density parameters on the influence of the temperature field, the largest natural fracture density of 0.66/m pre-fluid dosage is only 1/3 of 0.16/m. Therefore, for hydraulic fracturing of deep fractured reservoirs, it can be considered to optimize the amount and displacement of precursors from the perspective of cooling, so as to reduce the economic cost.

Competent Authorities：China National Petroleum Corporation Ltd

Sponsored by：CNPC Bohai Drilling Engineering Co. LtdPetroChina Huabei Oilfield Company

Editor-in-Chief：Shi-chun Chen

Address： Editorial Department of Drilling Fluid and Completion Fluid, Bohai Drilling Engineering Institute, Yanshan South Road, Renqiu City, Hebei Province

Postcode： 062552

Tel：（0317）2725487　2722354

E-mail： zjyywjy@126.com

CN13-1118/TE

ISSN1001-5620

LinksMore

Email Alert RSS