The Yantata formation in the Vibora Field in Bolivia is a very fine grained, friable sandstone at 8500 ft depth. As an alternative to frac-packing, “fracturing for sand control” was attempted. The first “fracturing for sand control” completion produces more gas and condensate than the majority of gravel packed wells, does not produce sand (despite the absence of a screen or gravel pack), and has a simple completion to allow access to other formations for future work.
This paper describes an experimental work in Hydraulic Fracturing performed on a gas reservoir that has a very thick friable sandstone, the object of which is to control the production of formation sand and optimize field exploitation.
The Yantata formation in the Vibora Field in Bolivia is formed of a very fine-grained sandstone that is poorly consolidated, with a thickness of 80 meters net average. It produces gas and condensate and has serious sand production problems.
In order to avoid the sand influx, the wells were produced with very small choke orifices for years, restricting the field's hydrocarbon production.
Lately gravel packing has been used with good results, but the great thickness of the productive reservoir leads to the need for more than one packing per well. This necessitates the use of complex and costly dual facilities that at the same time impede production in the same well of other two reservoirs present in the field.
The hydraulic fracturing was carried out on the VBR-24 well and was designed to open about 40 meters in height from the top of the reservoir, where only 7 meters were perforated and vertical communication was ensured for at least the top half of the total thickness of the reservoir, eliminating possible sedimentary barriers.
In order to neutralize sand migration a proppant covered with curable resin was used. The resin coating increases the strength of the sand grain to resist crushing and, as it cures in the formation, the coating bonds the individual grains together impeding flow-back and without reducing greatly the permeability.
The results obtained were successful because the well produces more gas and condensate than the majority of the wells that produce with gravel packing, it does not add sand and it has a simple facility that eases entry into the well for future interventions.
Author(s): Miguel Angel Casares, Juan Felipe Talavera, ANDINA S.A. - Bolivia
Paper Number: SPE 69584