This paper describes a method for fracture-stimulating noncemented horizontal wells in multiple stages. For existing openhole horizontal wells, an open-ended nonperforated liner is inserted nearly to the toe of the horizontal section. The liner is hung off inside intermediate casing, and the liner top is packed off. The liner is not cemented in place. The first fracture-treatment stage is pumped through the liner and out its end, creating a fracture near the toe of the horizontal section. Perforating guns are then positioned downhole to create holes in the liner at the next fracture initiation site. After perforation, the gun is removed, and the next fracturing stage is pumped at a high rate. This process is repeated for each treatment stage, spacing fractures along the horizontal interval.
Treatment diversion is accomplished with high injection rates and a fluid-friction pressure drop. The horizontal distance between fracturing stages is carefully designed for optimizing all diversion parameters and maximizing the effects of fluid friction in diverting fluid into each new perforation set. No special liner equipment, mechanical diversion equipment, or packers are used.
For an existing openhole horizontal completion, the design is based on the liner size, the diameter and number of perforations, the distance between perforations, and the injection rate required to achieve diversion. This technique is most effective when the hole size, pipe size, and horizontal length are in a specific range.
A circuit analogy of a parallel electrical circuit with multiple resistors graphically demonstrates the calculation of individual injection rates and treatment volumes required to divert the inj ection fluid through the various flowpaths into multiple sets of perforations.
In one field case, a high-volume fracture-stimulation treatment was pumped down intermediate casing into an open horizontal hole at a high rate. The post-fracture production was less than expected. Later, a solid liner was inserted into the open hole, and the operator used the frictional diversion technique (FDT) to distribute fractures at selected sites along the horizontal section. An incremental production increase, a lower decline rate, and increased reserves were obtained.