Hydrocarbon-based drilling fluid (HCBDM)

Main advantage of hydrocarbon-based drilling fluid (HCBDM) before other systems is that it has low content of output phase and high inhibiting properties. It prevents shattering drilling chips and reduces inflow of active solid phase into solution. HCBDM has low fluid loss indicator of 5-10cm3 for 30 minutes at temperature of 150-200ºC under bottomhole conditions. Relatively high structurally mechanical parameters and optimal deformation behavior of HCBDM allows efficient cleaning of wells from drill chips. The mud is represented by stable emulsion with high holding capacity that increases mud density up to 2100 kg/m3 by means of hydrophobic barites. Specified properties of HCBDM allow control of suability of well shaft with relatively low density that is lower than hydrostatic density. The use of HCBDM reduces risk of seizure of drilling tool under severe geological and technical conditions, improves condition and safety of drilling. Drilling mud has low content of clay phase and improves quality of primary revelation of producing horizons and retains their natural reservoir characteristics. Drilling mud has high lubricating properties and doesn't require special lubricating additives. HCBDM is easily cleaned from drilled chip at mechanical cleaning facilities, especially at the first stage (screen shakers). It doesn't absorb formation waters. Increase of the efficiency of mechanical treatment of the mud allows controlling of the content of solid phase within optimal range and retains stability of mechanical and rheological parameters. HCBDM can be used for drilling of the well within intervals, consisting of chemically active and highly colloidal clay. Thermal stability of HCBDM is 180 - 200°С. HCBDM is represented by colloidal system, where anhydrous phase (diesel fuel or mineral oil) and water are used in ratio of 60% 40% – 75% 25 % as a disperse medium. Ratio between anhydrous phase and water increases due to increase of mud density. Mud has stable system that is represented by stable invert emulsion. Procedure of preparation and adjustment of HCBDM parameters HCBDM parameters are prepared and adjusted in the course of drilling in accordance with developed procedure under the guidance of qualified specialists in drilling mud. Mud is based on mineral oil and sea water that are dispersive medium for chemical components of formulation. Components of drilling mud are added in strict sequence that is provided by technology of preparation of drilling mud with low water content.  Main initial parameters (density, viscosity, rheological and filtration characteristics) of prepared HCBDM should correspond to necessary requirements, specified in well construction project. Control and adjustment of parameters should be carried out in accordance with technological condition and technical abilities of mechanisms for adding of chemical reagents. Quality of cleaning of mud from drilling chips at mechanical cleaning facilities in very critical upon adjustment of parameters. High contamination of mud with excess solid phase results in deterioration of rheological properties. It is necessary to take measures for partial renewal of the mud with fresh portions of mud. Excess amount of mud should be cleaned again at centrifuge within several cycles for its reuse in drilling process.