2024 Vol. 41, No. 4

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FORUM
Progress in Studying Affecting Factors and Alkaline-Activated Reaction of Activity of Metakaolin
YIN Hui, LIU Huajie, JI Chengyuan, XUE Jialun, SUN Kai, LI Lingxi, ZHENG Shuangjin
2024, 41(4): 419-426. doi: 10.12358/j.issn.1001-5620.2024.04.001
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Metakaolin has many advantages such as low energy consumption, low calcium content and resistance to CO2 corrosion, and is a potential substitute for conventional silicate cement. By summarizing the progresses made in studying the factors affecting the activity of metakaolin and the alkali-activation reaction, the feasibility of applying metakaolin in well cementing is analyzed. In this paper the factors affecting the activity of metakaolin are summarized, such as calcination temperature, calcination time as well as the aluminum oxide and silica contents of metakaolin. If the calcination temperature is too high or too low, and if the calcination time is too long or too short, the activity of the metakaolin will be low. This paper also introduces the factors affecting the alkali-activation reaction and the components of the products of alkali-activation reaction. It is thought that shortcomings exist in the present research work, and the future researches should be focused on the application of metakaolin in well cementing. In future researches, more attention should be paid to the effects of experimental factors on the thickening time of metakaolin cement slurries and to the methods of how to enhance the compressive strength of the metakaolin slurries without introducing high-calcium materials.
DRILLING FLUID
Mechanism of Fluid Shale Interaction and Construction of Drilling Fluid System in Marine Land Transitional Shale Reservoirs
WANG Wei, WANG Jintang, XIN Jiang, CAO Zhenyi, LIN Wei, LIU Lei, SUN Jinsheng
2024, 41(4): 427-436. doi: 10.12358/j.issn.1001-5620.2024.04.002
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China possesses abundant shale geological reserves and a high concentration of resources in the coastal transition zone. However, drilling operations in this area are susceptible to wall collapse and instability, creating significant risks. This study investigates the mineral composition and microstructure of reservoir rocks through drilling core observation, electron microscopy, CT scanning, and X-ray diffraction analysis. The findings reveal that the shale gas reservoir is predominantly composed of quartz and clay minerals, with a clay mineral content of 45.7%. Notably, montmorillonite is absent, while kaolinite represents 35%, and the illite/montmorillonite mixed layer accounts for 26% of the clay minerals. The rock samples exhibit nano-scale pore development, micro-crack formation with widths in the micron range, and interconnected narrow cracks. Analysis of alterations in interlayer spacing, surface tension, linear expansion rate, and crack expansion after rock-fluid interaction unveils that shale in the coastal transition zone solely undergoes surface hydration, offering insights into the mechanisms of rock-fluid interaction in shale gas reservoirs. Consequently, a high-performance water-based drilling fluid system specifically designed for the coastal transition zone shale gas reservoir is formulated, encompassing the selection of water-based drilling fluid inhibitors, plugging agents, and lubricants. The system is subsequently subject to comprehensive laboratory evaluation, which substantiates its exceptional performance in terms of conventional properties, inhibitory effects, sealing capabilities, and lubrication. It demonstrates a temperature tolerance of up to 100 ℃, experiences a fluid loss of merely 6 mL under high-temperature and high-pressure conditions, exhibits a shale swelling rate of 1.03%, possesses an overall drilling fluid lubrication coefficient of less than 0.15, reduces API filtration loss by 40% compared to the base slurry after 30 min, and effectively seals micro-cracks in the reservoir formations. Additionally, the system demonstrates a low level of biotoxicity, with an EC50 value of 37,260 mg/L. It can meet the requirements of drilling fluid performance for transitional shale gas drilling operations between sea and land, and has been applied on site with good sealing and anti-collapse effects. This research addressing the considerable technical challenge of wall instability in the coastal transition zone shale wells.
Control Mud Losses into Carbonate Reservoirs with Polymer Gels in Tahe Oilfield
LI Liang, FANG Junwei, PENG Boyi, YU Peizhi, GENG Yunpeng
2024, 41(4): 437-443. doi: 10.12358/j.issn.1001-5620.2024.04.003
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Carbonate reservoirs in the Tahe oilfield are developed with fractures and vugs, drilling into vugs and lost circulation which in turn inducing blowout, borehole wall collapse and stuck pipe have frequently been encountered, and conventional bridging techniques cannot be used to effectively control the mud losses. To deal with the mud loss problem encountered in well workover and completion of old wells, a high temperature polymer gel lost circulation material (LCM) has been developed. Evaluation of the performance of the polymer gel LCM shows that before gelling, the viscosity of the polymer base fluid is in a range of 13 – 14.5 mPa∙s. At 150 ℃, the gelling time of the polymer can be adjusted between 30 min and 150 min. After gelling, the polymer gel loses its mobility and forms a high-strength gel plug. The polymer gel is tested on a 5 cm long iron-made core with 3 mm fractures, which simulates fractures found in the carbonate reservoirs, and a pressure bearing capacity of 2.1 MPa/42 cm is obtained. The polymer gel has good contamination resistance and good stability. The gel of the polymer can be easily broken, by adding alkaline solution into the gel to change the pH value, the gel becomes a low viscosity fluid in 48 h. After gel breaking, the permeability recovery of the rock cores that have been plugged with the gel can be greater than 85%. This high temperature polymer gel can be used to effectively plug formation pores and vugs, it can also be effectively removed away, thus making it a good choice for severe mud losses controlling in workover operations.
Ultra-Low Density Drilling Fluid Technology for Drilling Ultra-Deep Fractured Carbonate Reservoirs
ZHANG Shaojun, YANG Chengxin, ZHANG Yu, SHAO Changchun, LI Chengli, YU Huamin
2024, 41(4): 444-450. doi: 10.12358/j.issn.1001-5620.2024.04.004
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Ultra-deep wells with pressure coefficient less than 1.0 in Tarim oilfield are generally faced with lost circulation of mud in drilling the low-pressured carbonate reservoirs. These wells, with an average depth of over 6,000 m, have high risks of well control, thus, apart from drilling with no return when lost circulation is encountered, no other better means can be used to drill the wells to the designed depths, and in many cases, the wells can only be completed before drilling to the designed depths. To extend the lengths of the horizontal sections of the ultra-deep wells, researchers have developed high strength hollow micro glass beads for formulating water-based drilling fluids with density in a range of 0.93 g/cm3 to 1.07 g/cm3. This paper describes in detail the operation process of the well Zhonggu 262-H4C in which lost circulation was encountered and a low density drilling fluid was then used to regain circulation and drilling was resumed directionally to the designed depth. In the field operation, the density of the drilling fluid was reduced to 0.98 g/cm3, and additional 373 m was drilled after the circulation, realizing the geological goal of one well to penetrate two fractured-vuggy bodies. This measure ensures that the well to be drilled to the designed depth after encountering lost circulation, setting a precedent of drilling an ultra-deep well with vertical depth over 6,000 m using low density drilling fluid formulated with hollow micro glass beads, and providing a technical reference for drilling low-pressured formations in old oilfields in China.
The Lubricity of Amphiphilic Carbon Dots in Silicate Drilling Fluids
HE Dandan, LAI Lu, MEI Ping, LU Fuwei, WU Juan
2024, 41(4): 451-457. doi: 10.12358/j.issn.1001-5620.2024.04.005
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Silicate drilling fluids have strong inhibitive capacity and good environment protection property, but their poor lubricity limits their application. In screening good lubricating agents for silicate drilling fluids, extreme pressure (EP) lubrication tester is used to measure the coefficient of friction of silicate drilling fluid samples containing amphiphilic carbon dots and polyoxyethylene surfactant. The best lubricating agent selected is then tested with total organic carbon analyzer, dynamic light scattering tester and contact angle tester to analyze its mechanisms of lubrication. The test results show that the amphiphilic cardon dots have excellent lubricity and high temperature stability. A 5% sodium silicate (Na2SiO3) water solution treated has EP coefficient of friction of around 0.500. The solution is then treated with 0.3% amphiphilic carbon dots (C12-CDs), and the EP coefficient of friction is reduced to 0.065. After hot rolling the C12-CDs treated Na2SiO3 solution at 110 ℃ for 16 h, the EP coefficient of friction of the solution is further reduced to 0.063, that is, the EP coefficient of friction of the Na2SiO3 solution is reduced by 87.52%. On the other hand, the polyoxyethylene surfactant shows no effect on the lubricity of the Na2SiO3 solution. Further study shows that C12-CDs has excellent adsorption performance on the surface of the quartz sands, the surface tension of a C12-CDs solution (c = 100 mg/L) increases from 44.81 mN/m before the adsorption process to 64.03 mN/m after the adsorption process, the adsorption capacity is 89.23 mg/L. Particle size analysis shows that the C12-CDs can effectively reduce the particle sizes of the Na2SiO3 solution; the average particle size of the Na2SiO3 solution is reduced from 514 nm to 63.2 nm. The multi-hydroxy structure and the long hydrophobic chain on the surface of the carbon nuclei can improve the adsorption of the amphiphilic carbon dots on the surfaces of the drill string, the borehole walls and the silicate aggregates. The amphiphilic carbon dots as a good lubricating agent have good compatibility with silicate drilling fluids. Field application shows that C12-CDs can reduce the coefficient of friction of silicate drilling fluids by 86.34%, and are thus a good lubricating agent for silicate drilling fluids.
Development and Evaluation of a Calcium-Resistant Compound Bentonite
YE Jingliang, CHEN Juan, LIU Fulin, JIN Chunzheng, YANG Xianyu, CAI Jihua
2024, 41(4): 458-466. doi: 10.12358/j.issn.1001-5620.2024.04.006
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In underground diaphragm wall and pile foundation engineering operations, calcium ions from the concrete continually invade into the drilling fluids because of the frequent contact of the drilling fluids with the concrete, leading to gradual deterioration of the basic properties of the drilling fluids and large amount of waste muds after the operations. To improve the calcium resistance of the drilling fluids and minimize the amount of waste drilling fluids produced, the natural bentonite used to formulate the drilling fluids needs to be modified. A calcium-resistant compound bentonite ACB-16 is synthesized with natural bentonite purified through high-speed centrifuging and monomers for polymerization, such as a hydrophilic monomer BX with double carbon bonds, hydrophilic monomers AS and AP with sulfonic acid groups. In the polymerization reaction, the monomers enter into the crystal spaces of the purified bentonite, reacting with each other through in-situ free radical polymerization. Studies on the polymerization products with FT-IR, particle size distribution test, SEM and TEM show that the monomers successfully in-situ polymerize in the crystal spaces of the bentonite. The quality of ACB-16 exceeds the quality of the OCMA bentonite. A drilling fluid formulated with ACB-16 has an apparent viscosity of 26 mPa∙s, an API filter loss of 7.6 mL, a good rheology and filtration property as well as a good calcium resistance. When contaminated with 1% calcium chloride, the rheology and filtration property of the drilling fluid are still stable. The limit of calcium resistance of a drilling fluid formulated with ACB-16 is 6,300 mg/L (equivalent to 1.75% CaCl2), perfectly satisfying the requirements for a drilling fluid to resist calcium contamination in foundation engineering. Using particle size analysis and SEM, the working mechanism of ACB-16 is studied. The high molecular weight polymers located on the networking structures of the bentonite hinder the ion exchange between the calcium ions and the bentonite, thereby maintaining the thickness of the hydration membrane and the c-spacing of the bentonite and supporting the network structures generated by the hydrated bentonite. Direct mixing of ACB-16 with water can obtain a calcium-resistant drilling fluid with excellent properties. ACB-16 is easy to use, it will have good application prospects in foundation engineering and other fields, and it can also be used in formulating anti-sloughing drilling fluids for high calcium environment such as salt and gypsum drilling.
Controlling Mud Losses into Deep Surface Formations of the Strike-Slip Fault Zone in the Tianhuan Depression in Ordos Basin
SUN Huan, ZHU Mingming, ZOU Shuang, TIE Mingliang, LIU Zhen, WANG Hao
2024, 41(4): 467-472. doi: 10.12358/j.issn.1001-5620.2024.04.007
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In recent years, with the increase of high-yield industrial gas flow wells in the Qingshimao area, this area has The Qingshimao block in recent years has become a high gas production area and will be the next important exploration block in Changqing Oilfield. Geologically the Qingshimao block belongs to the Tianhuan depression in Erdos Basin, with more and more deep exploratory wells drilled in recent years, lost circulation, especially severe mud losses in deep surface section of a well, has been more frequently encountered during drilling. The severe lost circulation is mainly encountered in the Quaternary System in which formation waters are very active, and conventional techniques for controlling the lost circulation are rarely effective. The Luohandong formation, on the other hand, has long section of continuously fractured formation, and the lost circulation is frequently encountered and the treatment is time-consuming. In dealing with mud losses in shallower water-bearing formations, a lost circulation slurry that expands when in contact with water is used to control mud losses. Large particles that can control the rate of mud losses have been developed and used to ensure one trip of drilling through the whole length of fractures. When drilling into stable formations, cementable lost circulation slurries with wide particle size distribution can be used to plug and seal off the long section of fractured formations. These practices have formed a special technology for controlling mud losses encountered in drilling the deep surface hole in the strike-slip fault zone in the Tianhuan depression in Erdos Basin. This technology has been successfully used in the Qingshimao block, and several wells with deep surface holes have been successfully drilled.
Fast Plugging Inhibitive Drilling Fluid Technology for Horizontal Drilling Through Bauxite Rocks
JIA Jun, CHEN Lei, HAO Chao, ZHOU Wenjun, FENG Yongbing
2024, 41(4): 473-480. doi: 10.12358/j.issn.1001-5620.2024.04.008
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Two wells, the well Long-XX and the well Ning-XX, in Longdong area are recently tested, and the target zone located in the bauxite formation has been found an important alternative resource for the Changqing Oilfield. Significant findings were obtained in exploring the bauxite formation through these two wells. Technical difficulties, such as prevailing of dissolution pores and fractures, borehole wall collapse, mud losses and poor hole cleaning etc. have been encountered in drilling the target bauxite formation. The main factors contributing to borehole wall collapse were found in analyzing and testing the bauxite samples for physical properties, chemical properties, mechanical properties and sensitivity characteristics, and a fast-plugging, inhibitive drilling fluid for safe drilling of the bauxite formation was developed. This drilling fluid has high temperature (170 ℃) high pressure filter loss of less than 10 mL and percent secondary cuttings recovery of greater than 91%. After soaking the bauxite samples in the drilling fluid and fresh water respectively for 15 days, the compressive strength of the samples tested in the drilling fluid is 81.8% higher than that of the samples tested in the fresh water. This drilling fluid has been tried in drilling the first horizontal Long-4XX well targeted the bauxite reservoir in Changqing, a horizontal section of 700 m was successfully drilled. The daily flowing production rate of this well is 3.53 × 106 m3, a new record made in developing the upper Paleozoic resources in the Erdos basin in the last 50 more years. This technology has provided a technical support to the development of the similar reservoirs.
Development and Application of a High-Strength Equilateral Tetrahedron Resin Solidifiable Lost Circulation Material
HAI Bo, LIN Xingjie, ZHONG Cheng, LU Yongzhi, WU Yuanpeng, HE Lun
2024, 41(4): 481-488. doi: 10.12358/j.issn.1001-5620.2024.04.009
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Lost circulation during drilling is a downhole problem frequently encountered in the Chuanyu area, and in part of the area, severe lost circulation encountered in complex formations can only be cured after several times of operation and with different lost circulation control techniques, resulting in high drilling cost. By analyzing the lost circulation control techniques used in the past, a one-sack temperature-control gel-type resin lost circulation material (LCM) YDFD was developed based on the principles of bridging and packing in fractures. The raw materials in producing the LCM YDFD include a high-strength equilateral tetrahedron resin as the main bridging material, a flaky resin and a thermo-set resin as the packing material, and a fiber material, and these three materials, by entanglement crosslinking, produce the final product YDFD. In lost circulation control, three models of YDFD, which are small, medium and large, are mixed in a certain ratio to combat mud losses of different rates such as mud losses into small fractures, vugs, big fractures and another type of mud loss called breathing loss. Into the LCM slurry a temperature control agent is used to regulate the time required for the LCM slurry to solidify, thereby ensuring safe operation and accurate plugging of the channels into which mud is lost. In controlling lost circulation with the YDFD LCM in the Chuanyu area, 93% mud losses are successfully brought under control in the first try. This technique is worth trying in combating mud losses in oil and gas development.
CEMENTING FLUID
An All-Liquid Spacer for LAS System
WANG Xueshan, ZOU Yiwei, ZHANG Fuming, TIAN Ye
2024, 41(4): 489-495. doi: 10.12358/j.issn.1001-5620.2024.04.010
Abstract(210) HTML (79) PDF (2418KB)(41)
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In well cementing operation, a certain amount of spacer needs to be pumped into the wellbore before injecting cement slurries. In offshore well cementing, the preparation of spacer requires heavy manual labor, and the labor intensity is quite high, resulting in low operation efficiency and poor control on the quantities of the spacer additives. To solve this problem, liquid additives are used to replace the solids additives in formulating the spacer, and the liquid additives are added through the additive addition system LAS. Using this technique, the traditional heavy physical labor in formulating a spacer is replaced with intelligent operation, the labor intensity is lowered, the efficiency of well cementing operation is increased, and the labor costs are reduced. A liquid spacer additive C-S70L is prepared through inverse emulsion polymerization. Using C-S70L as the core additive, a spacer suitable for injection using the LAS is formulated. This spacer can be used in temperature range of 20 - 120 °C and density range of 1.30 – 1.70 g/cm3. It has good suspending stability (no settling after hot rolling), a rheology that is easy to adjust, a fluid loss that is controllable and good compatibility.
Lithium Salt-Sulfoaluminate Slurry System for Negative Temperature Cementing
LIU Tao, DONG Sanbao, WANG Dan, GAO Fei, CHENG Xiaowei, FEI Zhongming
2024, 41(4): 496-505. doi: 10.12358/j.issn.1001-5620.2024.04.011
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Aiming at the problem that the strength of cement pastes commonly used in cementing under negative temperature environment develops slowly or even stops hydration, this paper studies the slurry properties of lithium salt (TSL) -sulfoaluminate cement (SAC) slurry system and the mechanical properties of cement stone at 4 ℃ and -10 ℃, and tests the hydration temperature rise and cumulative heat release of cement. The hydration process of cement was analyzed by X-ray diffractometer (XRD), thermogravimetric analyzer (TG/DTG) and scanning electron microscope (SEM), and the feasibility of application of TSL-SAC cement system in negative temperature cementing project was demonstrated. The results show that the slurry performance of TSL-SAC cement slurry system is well. When the content of TSL is 3% of SAC, the 48 h compressive strength can reach 23.01 ± 0.47 MPa at 4 ℃ and 3.98 ± 0.07 MPa at -10 ℃, which meets the requirements of cementing construction. At the same time, the hydration temperature rise and cumulative heat release of cement were effectively reduced by the introduction of temperature control materials. The maximum hydration temperature rise was reduced by 27.62%, and the maximum hydration temperature rise delay was 320.67%. The mechanism of TSL promoting the hydration reaction of SAC is that it increases the generation of gel hydration products of iron glue and aluminum glue in cement stone, promotes the growth and crystallization of AFt, forms a low crystallinity CaCO3 protective layer and reduces the carbonization of CH. TSL-SAC cement slurry has the potential of application in negative temperature cementing environment, and this study provides a certain experimental and theoretical basis for cementing in negative temperature area.
An Ultra-High Temperature High Density Corrosion Inhibitive Anti-Channeling Cement Slurry
ZHANG Fuming, XIAO Wei, ZHU Sijia, SHI Ligang, ZHAO Jun
2024, 41(4): 506-514. doi: 10.12358/j.issn.1001-5620.2024.04.012
Abstract(189) HTML (63) PDF (3925KB)(42)
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The oilfield in the west of the South China Sea, in which high temperature high pressure gas reservoirs are drilled, is a main gas production area. In this oilfield the formation temperature of the target zone in the Ledong area is 210 ℃, the formation pressure coefficient 2.20-2.29 and the safe pressure window only 0.04-0.05. These formation characteristics together with the existence of CO2 in the same target zone make it difficult for the energy to be explored and developed. One of the key technologies for the gas development in this area is the development of a corrosion-resistant cement slurry for use in ultra-high temperature high pressure environment. To efficiently develop the gas resource, a cement slurry, having its densities ranging between 2.40 g/cm3 and 2.60 g/cm3 and with CO2 corrosion resistance is developed. In this cement slurry, a reduced iron powder, a manganese ore powder and a silica of different particle sizes are sized and used as the solid material, a low activity MgO as the lattice swelling agent to prevent shrinkage of the cement sheath, a special latex as the corrosion inhibitor and anti-channeling agent, and an organic and an inorganic intercalated polymers as the high temperature suspending stabilizer. Laboratory evaluation experiment shows that under CO2 partial pressure of 50%, aging pressure of 100 MPa and aging temperature of 180-220 ℃, the compressive strength of the set cement after being corroded for 180 d is three times of the compressive strength of the set cement before being corroded. At the same time, the permeability of the set cement is only slightly increased (<0.01 mD). The hydration products of the cement change from C6S6H, an xonotlite before corrosion of the set cement, to CaCO3 and SiO2 after corrosion. The set cement, after being aged at 220 ℃ for 24 h, has compressive strength of greater than 25 MPa, and SPN value of less than or equal to 0.5. The thickening time of the cement slurry is easy to adjust, the cement is easy to flow, and the difference between the density of the slurry at the bottom and that of the slurry at the top is less than 0.01. These properties of the cement satisfy the requirements of the field operation.
Study on a Low Density Cement Slurry Capable of Preventing and Stopping Mud Losses and the Use of the Slurry
TIAN Ye, MA Chunxu, ZHAO Jun, CHEN Weixing, WANG Yixin, SONG Weikai
2024, 41(4): 515-521. doi: 10.12358/j.issn.1001-5620.2024.04.013
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The well Yuejin-3-3XC is drilled to a measured depth of 9,432 m, with length of the horizontal section exceeding 3,400 m. This depth and length of horizontal drilling has broken the record of the longest horizontal section in the deepest and ultra-deep horizontal drilling in Asia. The well Yuejin-3-3XC penetrated formations with complex geologic characteristics, and was difficult to drill. Requirements for the properties of cement slurries are high; high temperature, high pressure, low pressure bearing capacity of the formations drilled have all to be considered to avoid losses of the cement slurries. To deal with these difficulties, three low density cement slurries, which are C-Lo PSD (1.30 g/cm3), C-Lite STONE (1.60 g/cm3) and C-Hi PSD (1.40 g/cm3), are formulated. These cement slurries can be used in medium-low and high temperature conditions, and have been successfully used in cementing the well Yuejin-3-3XC. Compared with the cement slurries previously used, these three new slurries have mixing efficiency, rheology, suspension stability and compressive strength of set cement that are significantly improved. Among the three cement slurries, the C-Lite STONE (TBHC = 75 ℃/TTOC = 30 ℃) and the C-Hi PSD (TBHC = 145 ℃/TTOC = 105 ℃) have the strengths of the top slurries in 48 h of 81 MPa and 14.3 MPa under the temperature differences of 45 ℃ and 40 ℃, respectively. During drilling operation, the well Yuejin-3-3XC has encountered several times of mud losses. Use the self-made new lost circulation materials C-B62 and C-B66, the fractures into which the mud was lost were successfully sealed off, ensuring the smooth progress of the cementing operation.
An Anti-Corrosion Tough Cement Slurry Treated with Self-Crosslinking Epoxy Resin Emulsion
WANG Chunquan, YAN Haibing, DENG Tian’an, LIU Bo, YANG Dailin, TIAN Fabin
2024, 41(4): 522-530. doi: 10.12358/j.issn.1001-5620.2024.04.014
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The reaction between the acid gases such as H2S and CO2 with the hydrational products of silicates results in serious corrosion to the set cement, which is manifested in the increase in the permeability and dramatic reduction in the compressive strength of the set cement, negatively affecting the integrity of the wellbore. To deal with this problem, a self-crosslinking epoxy resin emulsion is developed to improve the ability of oil well cement to resist the corrosion by H2S and CO2. In laboratory study, the performance and the mechanisms of set cement to resist corrosion are evaluated at H2S partial pressure of 2.0 MPa and H2S partial pressure of 1.5 MPa, and the results analyzed. The results of the study show that: 1) Increase the concentration of the self-crosslinking epoxy resin, the compressive strength of the set cement increases; when the compressive strength of the set cement increases to a certain value, further increase in the concentration of the epoxy resin does not cause the compressive strength of the set cement to increase any more, it, on the contrary, causes the compressive strength of the set cement to decrease. The elastic modulus in this process decreases significantly. 2) As the concentration of the self-crosslinking epoxy resin increases, the corrosion depth caused by the H2S and CO2 gases in the set cement and the permeability of the set cement decrease, the compressive strength of the set cement first increases and then decreases. 3) The self-crosslinking epoxy resin can wrap up the hydrational products of the set cement, thereby isolating the set cement from being contacted with the acid gases and thus improving the corrosion tolerance of the set cement against acid gases. 4) Cement slurries treated with the self-crosslinking epoxy resin have good engineering properties, leading to reduced sensitivity of the thickening time of a cement slurry to the aging time of cement water, the concentration of the self-crosslinking epoxy resin as well as changes in temperature, and these make the technology easy to use in field operation. The anti-corrosion tough cement slurry has been used in the cementing of 6 wells, more than 90% of the well cementing job is classified as “excellent”, and 99% of the well cementing job is classified as “qualified”. From the study and the field operation it is concluded that the self-crosslinking epoxy resin emulsion fills and wraps up as a membrane the hydrational products of cement, rendering the set cement good anti-corrosion performance and toughness, and this makes the anti-corrosion tough cement very suitable for cementing wells drilled in the high sulfide content blocks in northeast Sichuan.
The Development and Application of Well Cementing Cleaning Agent DQQX-2 and Flushing Fluid Formulated with It
LIU Hao
2024, 41(4): 531-536. doi: 10.12358/j.issn.1001-5620.2024.04.015
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Residual oil based drilling fluids retained on the surfaces of casing strings and on the borehole walls become gels that are difficult to wash away, hence affecting the job quality of well cementing. To solve this problem, efforts were made on the development of flushing fluids for well cementing. By studying the physical properties of various cleaning agents for use in well cementing, a cleaning agent system with high cleaning performance and suspending capacity is developed. Based on the technical requirements for the well cementing pre-pad fluids, the suspending agent and other additives for a high efficiency flushing fluid are engineered. Laboratory study shows that in the flushing fluid when the concentration of the cleaning agent is in a range of 3% to 6% and the concentration of the suspending agent is 3%, the flushing fluid can function normally at 180 ℃, the density of the flushing fluid can be adjusted between 1.2 g/cm3 and 2.0 g/cm3, and the difference between the density of the top fluid and the density of the bottom fluid is less than 0.03 g/cm3 after the flushing fluid stands for 24 h at 23 ℃. The time for the flushing fluid to clean completely the residual oil-based drilling fluids is within 7 min. This flushing fluid has good compatibility with the drilling fluids and the cement slurries. Field operation results show that in wells cleaned with this flushing fluid, the cementing job is performed smoothly, and the excellent job quality of cementing the horizontal section of a well is more than 93% of the total. Field operation achievements prove that this flushing fluid can be used to better clean the wellbores drilled with oil-based drilling fluids and enhance the efficiency of displacing the cement slurries, thereby improving the job quality of well cementing.
FRACTUREING FLUID & ACIDIZING FLUID
Study on Desorption and Degradable Lotion Reducer
HUANG Jing, YAO Yiming
2024, 41(4): 537-545. doi: 10.12358/j.issn.1001-5620.2024.04.016
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In view of the high content of adsorbed gas in shallow normal-pressure shale gas, which is difficult to increase production and achieve effective exploitation, and the difficulty of natural degradation of conventional polymer drag reducer, oil-free lotion drag reducer was synthesized through aqueous dispersion polymerization. using friction meters, magnetic levitation balances, etc to evaluate the performance of drag reducr and their formed slick water systems The experimental results show that the laboratory resistance reduction rates of the 0.6% to 1.0% resistance reducing water system prepared with this resistance reducing agent are all above 70%, on site drag reduction rate of 84%. The desorption experiment results show that the desorption rate of the product reaches 85%, which is much higher than the conventional lotion drag reducer product. The natural degradation ability of the drag reducer was evaluated using the intrinsic viscosity method, and it was found that it can achieve natural degradation at 95 ℃ in 330 hours, with a degradation rate of 86%. The core damage rate is much lower than that of the guanidine gum system, and the IC50 test results show that the drag reducer is non-toxic and environmentally friendly at the concentration of use. This provides technical reference and new product ideas for the development of shallow atmospheric shale gas.
Characteristics and Application Prospects of Diutan Gum Fracturing Fluid
BAI Yan
2024, 41(4): 546-550. doi: 10.12358/j.issn.1001-5620.2024.04.017
Abstract(184) HTML (54) PDF (2253KB)(33)
Abstract:
The factory-like volume fracturing and continuous mixing for reservoir stimulation require the fracturing fluid to have better broad-spectrum performance and faster dispersion and sticking speed in terms of water quality. This article reports a surface modified diutan gum that can be directly used to prepare non-crosslinked fracturing fluids using formation water, seawater, and reinjection water. According to SY/T 5107—2016 《Evaluation Method for Performance of Water Based Fracturing Fluids》, the diutan gum and non-crosslinked diutan gum fracturing fluid was evaluated. The experimental results showed that it has good dispersibility, fast viscosity increase speed, and can reach maximum viscosity in 5～20 minutes in formation water, seawater, reinjection water, and pH 2～12 aqueous solutions, meeting the requirements of continuous mixing; 0.4% diutan gum fracturing fluid has good temperature resistance, shear resistance, high elastic modulus of network structure, excellent suspended sand performance, and can meet the requirements of 140 ℃ fracturing operation; The 0.4% diutan gum fracturing fluid is easy to break, with a residue of 212 mg/L, which is much lower than the industry standard of 600 mg/L and has less damage to the reservoir. Through the analysis of the prospects of using diutan gum fracturing fluid, it is believed that the use of formation water, seawater, and reinjection water to develop diutan gum fracturing fluid can achieve local water use for fracturing, reduce water costs and water preparation cycles; Diutan gum fracturing fluid is more suitable for the factory-like volume fracturing and continuous mixing requirements of alkali sensitive reservoirs and unconventional dense reservoirs.
COMPLETION FLUID
Development of Polymer Gel Temporary Plugging Agent and the Application
LIU Wentang, LIU Yutong, LI Xudong, LIU Yunfei
2024, 41(4): 551-556. doi: 10.12358/j.issn.1001-5620.2024.04.018
Abstract(216) HTML (72) PDF (2523KB)(46)
Abstract:
Laojun 4 Well is a high sulfur gas well located on the edge of Puguang, after acid fracturing, The formation pressure coefficient is low, before putting into production, the temporary plugging is necessary,but there has two Circulation valves stalled within 1m,the normal temporary plugging agents cannot smoothly pass through the inner diameter of the circulation valve.In view of the above problems, a polymer gel temporary plugging agent has been developed and successfully applied in Laojun 4 Well.Laboratory and field experiments show that the polymer gel temporary plugging agent has a plugging pressure of 27 MPa and a validity period of 15 days at 130 ℃, with the high plugging removal rate,it can block the gas escape from the wellbore. After being put into production, the output is about 1.2 million m3/d, the effect of site application is super.

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