Study Of Low Thermal Cementing Slurry Suitable For Deep Water Drilling

Deep-water means more than350meters sea area. Deep-water surface cementing have such problems:low temperature, low formation fracture pressure and the presence of gas hydrates.There are much challenges in cementing under this environment. Deep-water cementing technical difficulty mainly including:1)when water depth is deeper than1000m, the temperature will below4℃, after the conventional cementing cement hydration solidification performance is difficult to meet the requirements of low-temperature hydration;2) seabed mud offline stratum failure pressure low and need to have low density slurry matching stratum failure pressure changes;3) there may be hydrate within a certain depth.And it is difficult to cement,because the heat will cause hydrate dissociation.Develop low heat slurry to form low-temperature shallow stream efficient cementing structure casing is the key guarantee to effective development of slurry Marine deep-water exploration. Till now, there is no pure G slurry used in deep water level silicate cementing surface casing of the report in domestic. And the most difficult problem is low density condition; slow development water shutoff strength too long with curing phenomenon exists. The author suggests that overcoming the problems from the following three aspects to handle with deep-water low density slurry design.1) Use combination of organic early strength agent and inorganic early strength agent can make slurry effectively solidified in a short time. If want to make Portland cement with strength at low temperature, the first is to ensure water at low temperatures in the mud to effectively solidified in relatively short time. In deep low heat slurry system, use high low temperature early strength agent, improve the Portland cement hydration rate under low temperature, prompting strength at low temperature.2) Use of low density high-performance reduce agent, effectively increase cement gel materials in the proportion of water in mud. Deep-water surface water by low strata cementing slurry burst pressure limits, need to use density reduce agent. So when designing slurry, needs to choose high voltage low density reduce agent, to enhance the density reduce effect and improve cement gel materials in percentage of slurry, and promote the cement stone strength, moreover, the high voltage ease for cement paste. The agent can contribute effectively support intensity, relative improve low density slurry early strength. 3) Effectively reducing the cement stone penetration, increase cements stone intensity. Variety of solid particle existing in low density Portland cement slurry, particle, there are gaps in the slurry after curing, these gap affects the cement paste, the permeability and the strength of the cement paste. To improve the strength of the cement paste and lower the permeability of slurry, in low density in Portland cement slurry system, need to join good performance filling agent. This enhancement agent should include active filler material and inert filler materials, active filler material for a hydration active ultra-fine particle, these materials can promote cement hydration, effectively filling particles particle gap; And inert filler material can be able to more effectively fill the void, in both strengthening agent, cement used blends with the density of rock with early strength can get effectively improved.Through the screening evaluation, deep-water silicate cement slurry system components finally identified:G level cement, South China Sea water, CG88L Fluidloss agent, DWR-6,000beads ease, CF415L dispersant, PF strength agent, C16exothermic suppression materials. Because the sedimentary rock formation time is short, the lack of adequate overlying strata, the stratum structure loose makes low failure pressure undersea strata, usually with low density slurry to cementing deep-water surface. In order to achieve the best cementing effect, for different deep-water stratum failure pressure in the opposite sex, there should be in cementing for cementing stratigraphic design corresponding slurry density. Through the adjustment of water in mud reduce agent, strengthening agent and the mixed water, determine the1.30～1.60g/cm3slurry formulation as follows.1.30g/cm3slurry formulation:100%G level cement+90%seawater+10%PF (strengthening agent)+6%(superfine cement)+1%(defoamer)+1.60ACC (coagulant)%+3%CF415L (dispersant)+28%DWR-6,000(lightweight additive)+4%CG88L (Fluidloss agent)+12%C16(exothermic suppression materials);1.40g/cm3slurry formulation:100%G level cement+82%seawater+10%PF (strengthening agent)+6%(superfine cement)+1%(defoamer)+1.60ACC (coagulant)%+3%CF415L (dispersant)+20%DWR-6,000(lightweight additive)+4%CG88L (Fluidloss agent)+12%C16(exothermic suppression materials);1.50g/cm3slurry formulation:100%G level cement+77%seawater+10%PF (strengthening agent)+6%(superfine cement)+1%(defoamer)+1.60ACC (coagulant)%+3%CF415L (dispersant)+13%DWR-6,000(lightweight additive)+4%CG88L (Fluidloss agent)+12%C16(exothermic suppression materials);1.60 g/cm3slurry formulation:100%G level cement+64%seawater+10%PF (strengthening agent)+6%(superfine cement)+1%(defoamer)+1.60ACC (coagulant)%+3%CF415L (dispersant)+10%DWR-6,000(lightweight additive)+4%CG88L (Fluidloss agent)+12%C16(exothermic suppression materials)Through the screening evaluation, deep-water silicate cement slurry system components finally identified. In which G level for Ge zhouba production of cement is G level of Portland cement; CG88L Fluidloss agent is AMPS polymer drop relative molecular weight lost agent, in10million-200000; DWR-6,000reduce agent for hollow boric acid calcium salts beads, silicon is low alkaline, density is0.42g/cm3,70MPa pressure in the continued survival rate at retro-refractive90%; CF415L dispersant is polystyrene sulfonic acid salt solution and making-1, SSE-1, a mixture of SAE-2, etc; PF enhancer can greatly facilitate the hydration of Portland cement at low temperatures; C16can balance the heat which cement hydration released, and can control the heat below a certain temperature.The water we used is south China seawater.After the water system evaluation of the slurry for formulation performance, have found:whether thickener time, cement strength or hydration exothermic, coagulant agent to join can effectively improve cement strength, speed up the cement hydration exothermic to improve cement early strength. Judging from the performance evaluation, coagulant agent to join the rheological property of virgin pulp, density, thickener curve has certain improvement action; The strength of cement stone with strengthening agent concerned, with mixed coagulant agent to join, can be improved obviously, in hydration coagulant agent and strengthening agent for improving early cement strength joined with better effect.