As concerns about hazardous effects of using conventional Oil Based Mud (OBM) have been intensified in Iranian offshore fields, companies are looking for environmentally acceptable substitutes that possess the technical advantages of OBM and remain in satisfactory price range. One of the highest prospects, as an alternative for OBM, especially in deep water and deviated offshore drilling, is Synthetic Based Mud (SBM). Paraffin is a type of synthetic fluid that can be extensively utilized in Iran due to its lower cost and availability with respect to other types of synthetic fluids. Developing a suitable, less expensive formulation for this innovative system by relying on local products is highly demanded.

In this study, feasibility of replacing OBM with more environmentally acceptable Paraffin Based Mud (PBM) was investigated. Suitable formulations for PBM at desired operational ranges of temperature, Mud Weight (MW) and Synthetic to Water ratio (S/W) were developed. In addition, Rheology properties and Electrical Stability (ES) of the systems were measured. To examine mud stability under down-hole conditions, each system was hot rolled for 16 hours. The filtration characteristics of each mud sample were determined by means of a High Pressure High Temperature (HPHT) filter press. Furthermore, Shale recovery was evaluated, using highly reactive shale samples of KAJDOMI formation. The effects of possible contaminants in the system were also studied. Confirmation of the obtained results was conducted by comparison of PBM with similar conventional oil based packages.

Laboratory results indicate that from technical points of view, conventional OBM can be replaced with PBM in Iranian offshore fields since it suppresses environmental concerns and can provide technical advantages of OBM with reasonable cost. Comparisons of PBM with OBM show that rheological properties and shale recovery were approximately identical, while PBM represented higher ES and lower filtration rate that illustrates its better emulsion stability.

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