Three-part strategy eliminates an intermediate string ///

Taking an engineered approach to lost circulation issues helped eliminate the need for a 7-in. intermediate string on the Mestena Operating, Ltd. La Presa 5 well in Brooks County, Texas, Fig. 1. Two offset wells with similar profiles had lost the battle to severe lost circulation in the Vicksburg sandstone, requiring the operator to routinely factor in $500,000 per well for intermediate casing. The two offset wells, drilled with the same rig using conventional lignosulfonate drilling fluid, were planned with 95/8-in. surface casing at around 3,000-ft MD, a contingency intermediate string at about 7,000 ft to case off the Vicksburg thief zone, and a target depth of about 8,500 ft. Severe to total lost circulation and differential sticking-common problems in South Texas drilling operations even on relatively shallow wells-plagued the La Presa wells. A proposal was made by the drilling-fluids company to change the fluid type, flow rate and lost circulation treatments.

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