| The swelling and hydration of clay can lead to the instability of wellbore,and the addition of clay hydration inhibitor into the water-based drilling fluids can effectively reduce the occurrence probability of borehole instability.Clay swelling inhibitorcould be used in clay hydration expansion stratum,polyethereramine is one of the main research directions of clay hydration inhibitors.However,the inhibition clay hydration of polyethereramine is not complete and the resistance to temperature was poor.Clay hydration dispersible inhibitors can be used in clay water-dispersible formations,the coated polymer can inhibitive the dispersion of clay hydration,but it is difficult to apply in the high solid content water-based drilling fluids.Clay hydration swelling inhibitors and clay hydration dispersing inhibitors can be used in combination in readily expandable clay minerals and brittle clay mineral formations.With the increasing demand for water-based drilling fluids and the increase of shale gas drilling engineering,the development of strongly inhibitive water-based drilling fluids is particularly important.Therefore,the application of clay hydration inhibitors which can be used in high-density water-based drilling fluids,and strong inhibitive water-based drilling fluids suitable for using in different hydration formation is a promising development.In this paper,clay hydration swelling inhibitor Gemini-DHEDB and,low molecular weight clay hydration dispersing inhibitor PDWC,which are not reported in the literature have been synthesized and used in combination.A clay hydration inhibitor system DSP for the simultaneous formation of expansive clay minerals and brittle clay minerals was developed.The objects and boundary of the blocking agent and inhibitor in the strong inhibitive water-based drilling fluid were defined for the first time,and a high density and strong inhibitive water-based drilling fluid was developed with DSP as the core treatment agent.The main contents of the thesis are as follows:1.Synthesis and mechanism of Gemini surfactant Inhibitor Gemini-DHEDB.(1),Based on expansive clay mineral hydration expansion mechanism,a novel Gemini surfactant as a shale inhibitor,N,N'-ethylene bis dodecyl(2-hydroxyethyl)aminium bromide(Gemini-DHEDB)was prepared with diethanolamine,bromododecane and dibromoethane as raw materials.The structure was characterized by FT-IR,1H NMR,melting point meature and elemental analysis.The swelling height of sodium bentonite(Na-MMT)in deionized water and the rolling recovery(100?×16 h)was 18.139 mm and 18%,respectively.Results showedthat the inhibition performance of 2.0 wt%Gemini-DHEDB was better than the same mass of DMDAAC,tetrabutylammonium bromide and trimethyl 2-hydroxyethylammonium bromide.Gemini-DHEDB can inhibit the hydration and expansion of clay to achieve the performance of polyether amine,the clay hydration dispersion ability of 2.0 wt%Gemini-DHEDBwas stronger than polyether amine.The temperature resistance of Gemini-DHEDB was better than polyether amine and other several small molecule inhibitors,the large decomposition temperature of Gemini-DHEDB was about 200 C.(2),The inhibition mechanism of Gemini-DHEDB was studied,and the results show that Gemini-DHEDB can be physically and chemically adsorbed with Na-MMT and can effectively change the mi-crostructure of Na-MMT.The dry and wet Na-MMT inter-spacing was 1.28 nm and 1.94 nm,respectively.The dry Na-MMT crystal layer spacing treated by 2.0 wt%Gemini-DHEDB was 1.63 nm,which indicating that Gemini-DHEDB was successfully intercalated into the clay interlayer.The crystal layer spacing of wet Na-MMT treated with the corresponding concentration of Gemini-DHEDBwas 1.52 nm,which showed that the Gemini-DHEDB has a strong effect on the pulling layer and excellent water repellency.The effect of clay hydration inhibition was mainly due to the following two points that:1,Gemini-DHEDB can compete with the clay surface water compete for adsorption sites,and then replace the combined water and adsorption on the clay surface;2,Gemini-DHEDB hydrophobically modifies the clay surface to prevent free water from approaching the clay.2.Synthesis and mechanism of low molecular weight zwitterionic inhibitors AS/THAAB/MMA(PDWC).(1),based on the hydration dispersion mechanism of hard brittle clay minerals,a low molecular weight zwitterionic inhibitors AS/THAAB/MMA(PDWC)was prepared by using a novel cationic monomer:trihydroxyethyl allyl ammonium bromide(THAAB),sodium allylsulfonate(AS)and methyl methacrylate(MMA)as polymerization monomers.The results of gel chromatography(GPC)showed that the molecular weight of PDWC was about 22000.The inhibition performance evaluation showed that The swelling height of sodium bentonite(Na-MMT)in 2.0 wt%PDWC and the rolling recovery(100?×16 h)was 6.7 mm and 91.6%.The clay hydration dispersion inhibition performance of PDWCwas stronger than the coating agent poly-ECH-DMA,PAM and FA-367.It was found that the compatibility between PDWC and conventional treatment agent was good,and the overall inhibition performance of the system could be improved obviously without changing the rheological properties of high density water-based drilling fluid.The main reasons for the effect of clay hydration inhibition were as follows:1,PDWC coating in the clay surface,separate clay and water,and to prevent clay hydration and dispersion;2,with there arehydrophobic estersin PDWC,PDWC can exclude the free water outof clay.(2),The mechanism clay hydration dispersion inhibition of PDWC was studied.The results showed that PDWC can form effective coating on the clay surface.Compared with the clay particle size in the fresh water based muds,the diameter of clay particles in the PDWC solution was obviously larger,which showed the excellent coating effect of PDWC.The interplanar spacing of dry Na-MMT and wet Na-MMT treated with 2.0 wt%PDWC was 1.29 nm and 1.92 nm,respectively,indicating that PDWC was more difficult to enter into the Na-MMT crystal layer.The results showed that PDWC played a nice role in suppressing the hydration and dispersion of clay.The main reasons were that the composed of "bundled" and"film-forming" onto the clay.The inhibition mechanism of PDWC was mainly that PDWC can coat in the clay surface of clay,and there by preventing the hydration dispersion of clay.3.Study on high inhibition water based drilling fluids(1),Based on the comprehensive analysis of the knowledge of various disciplines,such as geotechnical engineering,soil science and drilling engineering,this paper makes an discussion about the role of blocking agent and inhibitor.Based on the point view of soil science:combined water can not transfer water pressure,free water could transfer water pressure as the foundation.It is concluded that the clay bound water is the object of the inhibitor,and the free water is the target of the plugging agent.(2),With the clay hydration swelling inhibitor Gemini-DHEDB and clay hydration dispersion inhibitor PDWC as the basic treatment agent,combinated the two inhibitor,a"double suppression" clay hydration inhibitor system DSP,which possessd simultaneous inhibition of clay hydration expansion and hydration dispersion was developed.The optimal dosage of DSP in aqueous solution was 1.5 wt%,and the linear expansion height of Na-MMT and the recovery rate of cuttings was 3.08mm and 95.3%,respectively.(3),High density water based drilling fluids system was selected,of which the inhibitor was removed,and the application of DSP in the system was investigated.It was found that the compatibility of DPS with conventional drilling fluid additive was well,and the optimal dosage of DSP was 0.5 wt%.Under the premise that the rheological property of the original drilling fluid system was not changing,the inhibition ability of it can be greatly improved.The formula of the highly inhibitive water-based drilling fluid drilling fluid system was determined as follows:2.5%sea-water based water muds+0.2%NaOH+0.15%Na2CO3+0.3%PF-PAC-LV+2%PF-CMJ+1%PF-LUBE+1%PF-SMP-1+1%PF-LSF+0.5%DSP+2%PF-GJC+1%PF-GBL+0.1%PF-XC+0.3%XY-179(barite as the weighting agent to 2.2 g/cm3).The blocking,inhibition and rheology performance of the system were perfect,cuttings rolling recovery and Na-MMT atmospheric linear expansion height were 94.9%and 3.6 mm,resprectly.After the hot rolling experiment,the drill cuttings were sharp and angular,which showed the excellent inhibition performance of the new inhibitor system and the water based drilling fluids. |
PDF Full Text Request