Abstract
This paper presents operational results of the pilot test under near balanced conditions of a new foam drilling fluid developed by PDVSA-Intevep in an inclined well drilled in La Paz Field in Western Venezuela. The target formations were a fractured, depleted limestone formations of low pressure, and the reservoir contains highly fractured and hard rocks, known for deferred oil production due to flushing by lost circulation. Similar wells drilled with aerated fluids in the vicinity have shown very low rates of penetration, short bit lives, and instability drilling fluid in presence of contaminants such as salts and crude oil. Results indicated that the foam formulation provided a high stability in presence of crude oil and cement contaminations, and an excellent cleaning capacity in a 12-1/4" hole wherein minimum annular velocities of 45 ft/min were obtained. The physico-chemical properties of the foam allowed regenerating the fluid 76 times with minimal amount of additives. Besides, the average rate of penetration was greatly increased compared to wellbores drilled conventionally and the bit used lasted much longer than in a conventional well in the same reservoir. Finally, this formulation specially developed to withstand high volumes of contaminants proved to be an excellent drilling fluid for near or underbalanced operations with adequate characteristics and very good performance.
