A . R Moazzeni - Islamic Azad University- Omidieh Branch
M Nabaei - Islamic Azad University- Omidieh Branch
S Ghadami jegarlooei - Islamic Azad University- Omidieh Branch

Circulation losses have always been a serious and expensive problem to drilling industry. Even with the best drilling practices circulation losses do occur. In order to reduce such losses to acceptable level lost circulation materials (LCM) or seepage control materials (SCM) are used. Between the available LCMs Sized LCMs work better and Between Sized LCMs, they would work better that have optimum size distribution.The objective of this study was to evaluate and compare the performance of Limestone and Shellfish to determine the effect of size distribution on their ability to cure lost circulation in pay zone and finding an optimum size distribution for them with respect to formation characteristic byexperimental methods.Six types of size distribution for Limestone and six types of size distribution for Shellfish were tested with three types of simulated unfractured formation. The three types of unfractured formation used were composed of coarse marbles, medium marbles and fine marbles respectively. The used mud was OBM (oil base mud), which is more perfect for drilling pay zone. The experiments were conducted in the BMT equipment at a differential pressure of 100 psi and constant temperature of 16oC. The performance of each size distribution of each material on each formation type was determined. From these experiments, some graphs were obtained which show optimum size distribution of tested LCMs based on formation grain size in unfractured formations.

optimization- Lost Circulation-Limestone-Shellfish-Size Distribution