Research And Application On Solid Free Polymer Drilling Fluids System For Oil Shale Exploration

With increasing lack of the energy source, the exploiting resources are gradually augmented. Oil shale has been placed into development planning of reserve energy source in China, and begun detailed resource survey in Nong'an, Shulan, Huadian, Yitong, Meihe, and Jiaohe in Jilin province. Associative item"Research on strong rejection capability of solid free polymeric drilling fluid system"of the Geology Reconnaissance Station (in short of"GRS"), Jilin province, the purpose of this paper is to triturate drilling fluids, which can agree with the request of practical oil shale exploration. From detailed record supplied by GRS, Jilin province, the formation of six mining areas is mainly made up by mud shale, mud stone and shale, which are sensitive to water; and sandstone, siltstone, conglomerate, the agglutination of which is weak. In the process of drilling these formations, the always open questions are wall collapse, leak, loss, reducing, low core adoption and core polluted. To solve these problems, drilling fluids must have strong rejection capability, good rheological capability, powerful ability of protecting caving-in, well lubricity and so on. At the same time, wire-line core drilling technology with PDC bit adopted request that, mud cake can not be formed inside of pipe. Strong rejection capability of solid free polymeric drilling fluid system can satisfy these requests.In order to optimize experimental research, the orthogonal design is adopted in experiment. Through lots of experiments, seven bath formulas of four polymers drilling fluid system selected can satisfy practical production requirement. Four polymers drilling fluid system is silicate, polyvinyl alcohol (PVA), multiplicity of inorganic and organic polymer, polyacry lamide drilling fluid system. Seven bath formulas are as following:â‘ 22%Na₂O·nSiO₂+15%PHP+0.4%KCl+2.5%Na-CMC;â‘¡12.5%Na₂O·nSiO₂+2.5%PAC+0.4%KCL+7.5%PVA;â‘¢12.5%Na₂O·nSiO₂+2.5%PAC+0.4%KCl+2.5%Na-CMC;â‘£40%PVA+25%PAC-141+10%CMC+1.2%KCl;⑤40%PVA+10%PHP+1.5%KHm+4%KCl;â‘¥20%PVA+5%PHP+0.5%KHm+1%KCl+0.4%KOH+4%Na₂O·nSiO₂; ⑦30%PHP+1.5%KHm+10%CMC+1.2%KCl+15%PVA;The collapse prevention mechnism of every polymer is different, this lead to the difference of film velocity and film compactability, and the distinct of collapse prevention capability. To silicate, mesh structure of three-dimensional gelatum is formation through monomer condensation. This mesh structure hold the hole stabilization by stopping the fluids into the wall of hole. Because of the similar ingredient between silicate and clay soil, the velocity of adsorded film is fast. Adsoption film is formed by the adsorption of silicate on the face of shale. At the same time, the film is space structure, so the compactability of film is not very good. To improve the compactability of film, must be through the adsorption of high polymer.The test block immersed in the silicate drilling fluid for five days has little alteration, but for seven days, it has minute cracks. Removing the CMC and PHP of the system, the test block has cracks only for three days.This experiment prove that, the velocity of adsorded film of silicate is fast, but the compactability is not very good, high polymer can improve the compactability of the film.Through competitive absorption between PVA and water on the face of clay soil, PVA absorpts on the face of clay soil first, and forms film.The film hold hole stabilization by stopping the fluid out of wall of hole.The film is plane constructure, so the compactability is good. The absorption velocity of PVA is more slower than silicate, because there is no similar between PVA and clay soil. Immersed in the PVA drilling fluid for six hours, the test block begin to have cracks, but the crack is not expansion along with the time. This experiment prove that, film velocity of PVA is slower than silicate, but the compactability is better than silicate.The polyacry lamide hold the hole stabilization by the asorption of long-chain polyacry lamide on the wall of hole. The film velocity and compactability of polyacry lamide are worse than silicate and PVA, so its stabilization capability is worse than them. The stabilization capability of partially hydrolyzed polyacrylamide(PHPA) is better than polyacry lamide(PAM), because of the difference of molecular structure. The test blocks immersed in the PHP drilling fluid begin to have cracks for three hours, but in the PAM drilling fluids for two hours. At the same time, the stabilization capability of PHP is effected by hydrolyse and molecular weight.The IPC (IPC for short instability prevention capability) of the solid free polymer drilling fluid systems was the result of synergistic action of the inorganic and organic polymers. The velocity of the adsorbed film and density of the protective foil were the key factors to determine the IPC of the solid free polymer drilling fluid systems.Selected bath formulasâ‘ and⑦put in use in six mining areas of Nong'an, Shulan, Huadian, Yitong, Meihe and Jiaohe. Productive practice proves that, the hole is stabilization, the inner of the hole is clear, the core of rock and mining is full, the adoption rate of rock and mining core can oversize 95%. The triturated solid free polymer drilling fluid can satisfy the request of drilling work, and has got preferable technique technology and economy effect by its application into the hale exploratory hole nearly 6000 meters.Directed problems exsiting in productiong work, research on emulsification of solid free polymer drilling fluid have been proceeded. The purpose of emulsification experiment is to emulsify the selected bath formula, advance the lubricity of the drilling fluid. On the basis of selection suitable emolsifier, HLB and emolsifier adding, silicate polymer, PVA and PHP can be emulsified. At the same time, the influence of every finishing agent on adorption mechanics of emolsifier is different, leading to different interfacial film. This is the key factors of latices stabilization. The addition of silicate may adsorpt emolsifier, and inhibit or damage the formation of interfacial film. This is not good to latices stabilization. High polymer CMC and PVA promote the formation of interfacial film, improve the strength and brace. This is good to latices stabilization. On the improving the latices stabilization, PAM is better than PHP, because of the different of molecular structure. The experiment prove that, it is feasible to emulsify solid free polymer drilling fluid.