Research On A Low Temperature And Low Hydration Heat Cement Slurry System

Resources of gas hydrate are rich in deep sea region. Speeding up the exploitation of gas hydrates are important energy development planning around the world. The development technology of natural gas hydrate as cutting-edge technology is separately advanced in China’s medium and long-term development plan of science and technology. Stability existence of gas hydrate is only at a certain scope. How to avoid instability when cementing the gas hydrate layer and safe exploitation of natural gas hydrate resources are a new request of cementing. Our country in natural gas hydrate layer cementing technology research is still a zero. In order to meet the development strategy of China’s oil and gas resources, basic research of cutting-edge applications, this is carried out in this study. Gas hydrate cementing is faced with the low temperature, instability of gas hydrates, shallow water-gas flow problem. Thesis is the first to conduct research about the low hydration heat of cement system, the small heat-affected cement accelerator, the low hydration heat cement endothermic agent, fluid loss agent, anti-gas channeling agent, etc.Based on the mechanism of hydration of Portland, micro-aggregate effect, morphological effect and pozzolanic reaction, the low heat performance foreign admixtures are introduced into the class G oil well cement in order to dilute the high hydration heat compositions of cement clinker, thus reducing the overall hydration heat of the cement system. Under the guidance of hydration mechanism of the cement clinker and activation theory of the low hydration heat materials, the thesis has optimized low hydration materials for deep water hydrate layer cementing, has evaluated hydration heat of materials with low hydration heat, cement slurry thickening time, rheology and strength of cement stone, etc. And a cement formulation of separately adding low hydration materials has been acquired.Two or more cementitious materials added into cement at the same time are available to the complementary performance advantages. Therefore, the low hydration heat preferred materials （slag, fly ash） simultaneously are added into cement, then forms an low hydration heat of cement formulation LHC-3: slag, fly ash of 15%, Shengwei class G cement 70%. Its fibrous actinomorphic generated C-S-H gel has the largest number, it can maximumly fill and compact the cement micro-gap, enhance the strength of cement paste, furthermore its strength is equivalent with slag - cement system. And the hydration heat of LHC-3 cement system is lower, Cement slurry temperature only rises 11℃than the initial temperature, in contrast G class increased by 23℃than the initial temperature of cement. Therefore, LHC-3 achieves a better optimization of performance advantages in cement strength and hydration heat of cement slurry.Although LHC-3 has a greater advantage of performance cement, its cement strength can not fully meet the requirements of deep water hydrate layer cementing. The dissertation has researched how to excite the potential activity of the low hydration heat materials and how to improve the cement strength. The separate use or the compositional use of alkaline activator, sulphate activator, organic activators can inordinately excite the potential activity of the low hydration heat materials, and they has early strength acceleration to make cement stone acquire higher early strength. But they their hydration heat are so high not conducive to the stability of hydrate.Deepwater low temperature causes the slow solidification of construction cement, and it can extend construction cycle of oil and gas well. In accordance with Mannich reaction principle, amine with Hydroxyl functional group has aminomethylation and generate the Mannich alkali accelerator DWGZ-1. The accelerator has a small dosage（0-0.05%）, while the traditional accelerator is used between 1.0- 3.0% dosage; it has a strong accelerating effect for cement system of low hydration heat and makes cement slurry right-angle thickening（The traditional accelerator does not）. DWGZ-1 has a small hydration heat impact on the cement slurry system. Therefore, DWGZ-1 has unparalleled advantages with similar accelerators, and it can better meet the requirements of deep water hydrate layer cementing.Based on the principles which the inorganic salts with crystal water will absorb environmental heat when hydrate is losing its crystal water, with ethyl cellulose as the wall material and KAl（SO₄）₂·12H_O or CaSO₄·2H₂O as capsule-core, The use of microencapsulation technology has packaged the inorganic salts with crystal water, and successfully prepare the cement endothermic agent DWGCX of a low heat hydration. Absorption heat of the agent has a temperature selection, it can absorb heat of the Environment which the temperature is higher than 60℃. It will enable the slurry to maintain the temperature at around 60℃, without affecting the normal hydration of cement slurry, also avoiding the deep geothermal impact on the hydrate.In connection with particularity of deepwater hydrate layer cementing and adaptability of low temperature and low hydration heat cement, matched additive system of low temperature and low hydration heat has been researched and developed. Under low temperature Filmformed fluid loss agent DWGJ-2 has good low temperature performance and reducing fluid loss performance, and it does not affect the thickening time of cement slurry. The latex micro- particles and film-forming properties of anti-gas channeling agent DWGJR make it have good anti-gas channeling performance. It can strengthen the reducing fluid loss performance of fluid loss agent, it can improve cement penetration, and it can improve the corrosion resistance of cement.The low temperature and low hydration heat cement slurry system DWGC can better control exothermic hydration heat of the slurry, have good flow properties. Its thickening time can adjust according to cementing requirement. Its transition time of static gel strength is short and the probability of gas or water channeling occurrence will be decreased. Under the effects of the matched additives, cement strength and corrosion resistance got improved, it will help extend the life of oil wells. DWGC system can well adapt to the requirements of deep water hydrate layer cementing.