| In order to maximize productivity, low permeability oil and gas field will often choose the fractured horizontal well completion method to develop, due to the particularity of cementing operations, resulting in the casing running and centralization difficulty, the cement slurry in horizontal section is difficulty to cementing effective, drilling mud cake is difficult to completely remove, horizontal section of setting cement shrinkage it is not easy to control, cement slurry filtration and free fluid control requirements it is difficult to meet, the set cement during the perforating and fracturing is easy to be broken and other problems. Thus, requirements of cement slurry has good fluid migration control performance, excellent thickening solidification performance, firm cementation performance, moderate microswelling performance, good filtration control and free fluid control performance, especially with excellent flexility.To ensure low permeability oil and gas well completion work smoothly, improve cementing slurry settlement stability, eliminate the horizontal well drilling cuttings bed and slurry free liquid effect, reduce cement slurry filter and leakage of reservoir pollution risk, ensure the slurry to form an effective tube column and formation sealing, effective the formation and stratigraphic separation, control and elimination of horizontal well reservoir fluid improves cementing quality, improve cement stone in the perforating and fracturing process in high impact integrity, low permeability oil field development cost, enhance the efficiency of oil and gas field development, carry out the low permeability reservoir water cement slurry technology research. Through sufficient investigation due to increasing production operation at home and abroad, especially the fracturing operations, leading to the cement ring damage event, from the cement slurry system defects and the construction procedure in terms of analysis of damage reason, for low permeability oilfield fracturing well cementing design basis; On this basis, put forward to raise the method of cement stone tenacity:1. The scientific, effective evaluation methods. In addition to the conventional mechanical properties evaluation, and field perforating test is also innovative introduced to the interior evaluation category by us. Through the highly simulated field perforating test, from qualitative and qualitative different perspective to the evaluation of the cement stone tenacity.2. In adding to latex cement slurry system。Latex is a kind of elastic particles, it can be uniformly dispersed in cement slurry system and filled the cement pore and crack, latex particles and cement bond at the same time, meanwhile the latex particles are bonding each other, throughout the matrix structure in the formation of a elastic reticulate body, avoids the cement stone in the high-energy impact under the strain of stress concentration, effective guarantee for the integrity of the cement stone; At the same time, latex formed network structure can reduce the filtration system performance.3. The addition of fiber cement slurry system.Ordinary cement matrix is a brittle material, the tensile strength is low, and because of the existence of internal defects and often difficult to ensure tensile strength, adding fiber can make its tensile strength and ensure the full; When the cement stone under external impact cracks, the fiber in the cracks may be stretched out or fracture, this way may consume a large amount of energy, playing a very active role to prevent crack extended, thus greatly improve the cement stone crack resistance of breaking toughness, so that the cement under the action of external force performance a good flexible property.4. Effectively reduce the cement permeability, improve the strength of cement. mpact of low filtration free cement slurry has numbers of solid particles, where exists voids after, these voids affect cement permeability and cement stone strength. By reducing the permeability of cement slurry to improve the strength of cement stone, requiring adding a certain amount of the good performance of the filler into impact resistance low filtration free liquid cement system. This enhancer should include active filler material and inert filler material, the active material is a kind of hydration activity of ultrafine particles, can promote the cement particles hydration, effective filling granular space; And inert filler material to effectively fill the void. Compounding the two enhancer to use,can effectively improve the compactness of the cement and the early strength.In the cement slurry design guidance, according to API and construction standards on toughness cement experimental method, combining independent research and development of indoor simulated field perforating protective device, success on the field perforating process was simulated. After a lot of test screening, and ultimately determine the impact of low filtration free liquid cement slurry additive: CG88L filtrate reducer, CGR66L, CF44L, H21L-M latex dispersant retarder, CJ56L latex stabilizer, MCSEAL pore proppant,5.5mm Du pulls the fiber and PF-2enhancement agent.Horizontal well in well cementing process according to different fracture pressure of formation need to design the corresponding density cement slurry with a view to the borehole stability conditions, to achieve the best sealing effect.In the design of cement slurry slurry density regulation is simple and convenient sex should be considered. Interior through a series of experiments, by adjusting the water reducing agent, strengthening agent in the slurry and a mixed water proportion, construction of1.50～1.90g/cm3cement slurry.1.50g/cm3cement slurry formulation:100percent (JiaHua Class G cement)+22percent lightening admixture+12percent PF-2(reinforcing agent)+0.5percent EXP-1(expanding agent)+45percent fresh water+6.0percent CG88L(reduction agent)+0.4percent CF44L(dispersing agent)+0.7percentH21L-M(retarder)+1.0percent (latex stabilizing agent)+0.8percent CX601L(defoamer)+5.0percent CGR66L(latex)+0.2percent5.5mm Durafibre+6percent MCSEAL (pore support agent)1.60g/cm3cement slurry formulation:100percent (JiaHua Class G cement)+13percent lightening admixture+10percent PF-2(reinforcing agent)+0.5percent EXP-1(expanding agent)+42percent fresh water+6.0percent CG88L(reduction agent)+0.4percent CF44L(dispersing agent)+0.6percentH21L-M(retarder)+1.0percent (latex stabilizing agent)+0.8percent CX601L(defoamer)+5.0percent CGR66L(latex)+0.2percent5.5mm Durafibre+6percent MCSEAL (pore support agent)1.70g/cm3cement slurry formulation:100percent (JiaHua Class G cement)+6.0percent lightening admixture+6.0percent PF-2(reinforcing agent)+0.5percent EXP-1(expanding agent)+38percent fresh water+6.0percent CG88L(reduction agent)+0.4percent CF44L(dispersing agent)+0.5percentH21L-M(retarder)+1.0percent (latex stabilizing agent)+0.8percent CX601L(defoamer)+5.0percent CGR66L(latex)+0.2percent5.5mm Durafibre+6percent MCSEAL (pore support agent)1.80g/cm3cement slurry formulation:100percent (JiaHua Class G cement)+0.5percent EXP-1(expanding agent)+36percent fresh water+6.0percent CG88L(reduction agent)+0.4percent CF44L(dispersing agent)+0.45percentH21L-M(retarder)+1.0percent (latex stabilizing agent)+0.8percent CX601L(defoamer)+5.0percent CGR66L(latex)+0.2percent5.5mm Durafibre+6percent MCSEAL (pore support agent)1.90g/cm3cement slurry formulation:100percent (JiaHua Class G cement)+0.5percent EXP-1(expanding agent)+45percent fresh water+6.0percent CG88L(reduction agent)+0.4percent CF44L(dispersing agent)+0.45percentH21L-M(retarder)+1.0percent (latex stabilizing agent)+0.8percent CX601L(defoamer)+5.0percent CGR66L(latex)+0.2percent5.5mm Durafibre+6percent MCSEAL (pore support agent)The interior of the cement slurry properties were systematically study evaluation.By the existing experimental data:impact of low filtration free liquid cement slurry system under the condition of60centigrade has high early compressive strength, low filtrate loss, good rheological and thickening properties and impact toughness; Slurry dehydration<30ml/60centigrade,60centigrade/24hr curing strength19MPa; Comparing with polymer cement slurry system, impact resistant low filtration and free fluid system of the cement stone impact toughness increases above40%, interfacial bonding capacity is improved by more than60%, while the system of anti channeling ability has been greatly improved; In order to verify the system’s toughness, adopts field perforating perforating ejection hole after testing permeability, polymer cement stone perforation and permeability for0.0132mD/632mD; Impact of low filtration and free fluid system of cement stone and permeability for perforating:0.0084mD/76mD.The results show that the impact of low filtration and free fluid system has good resistance to damage of toughness, meet low permeability reservoir horizontal well fracturing completion requirements. |
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