*Assistant Professor, Department of Petroleum Engineering, DUIET, Dibrugarh University, Dibrugarh-786004, Assam, India
**Associate Professor, Department of Petroleum Technology, Dibrugarh University, Dibrugarh-786004, Assam, India
Online published on 20 July, 2015.
One of the most important elements of oil and gas well drilling process is drilling fluid or drilling mud. To remove cuttings from well, to suspend the cuttings and weighting material when circulation ceases and release them, to transmit hydraulic energy to clean the bit and the bottom of the borehole, to maintain wellbore stability, to minimize damage to the pay-zone, to minimize environmental impact, etc. are the most important functions of drilling fluids. All these functions are connecting to the rheological properties, filtrate & particle invasion and mud-cake quality of drilling fluids and all are more or less controlled by the clay component in conventional Water Base Mud (WBM). Non Damaging Drilling Fluid (NDDF) is an environmental friendly polymer mud system mostly used in pay zone sections of development wells and specifically in horizontal drilling to avoid formation damage. Non degradable compositional fine solid like clay, barite, etc. are not used in NDDF to counter the formation damage as well as environmental pollution. So, to provide the above mentioned properties in drilling fluid to perform the above mentioned functions, the XC-Polymer (with some assistant constituents) is used in NDDF instead of the non degradable clays. XC-Polymer (XCP)/Xanthan gum is a polysaccharide secreted by the Xanthomonas Campestrisbacterium which can be used in drilling fluid where formation protection, solids suspension and improved borehole cleaning are the primary concerns. It provides non-Newtonian rheology in WBM which is extremely necessary due to the flat velocity profile it creates in annular flow required for effective cuttings lifting in lower density muds. It is susceptible to bacterial attack and has great tolerance for salinity, fair tolerance for hardness ions and high pH and starts to degrade around 200 to 250°F [93 to 121°C] temperature. In this work, an attempt has been made to study the effect of varying composition of XCPon the different properties of laboratory formulated NDDF and choose its optimum composition based on the required mud parameters of the study area. This paper reports the effect and optimum composition of XCPas a rheology as well as fluid loss control component in the NDDF.
NDDF, XC-Polymer, Mud Rheology, Filtration Loss, Formation Damage, Geleki Oilfield
