Abstract

The clear increase of the gas and gas condensate reserves at the Eastern part of Venezuela during the last decades can be considered as the best evidence of the current huge efforts to develop those gas potential. More than 65% of the remaining gas reserves are concentrated in the Eastern part of the country, most of which show an initial reservoir pressure equals to or greater than the dew-point pressure, the reservoir temperature is between the critical and the cricondentherm temperatures, and the hydrocarbon mixture originally exists as a single-phase dew-point gas. As a result this would suggest " in-situ?? liquid drop-out between 2 to 12 percent which then after would hinder the natural gas production.

This paper shows the obtained results from studied cases of some routine or cyclic dry gas injection in wells of carbonate reservoirs. It has been concluded from the course of study that it is possible to re-evaporate the condensate liquid, especially around the wellbore through changing the composition of the in-situ liquid drop-out. This micro-compositional effect upon the liquid drop-out in the porous media within the vicinity of the well-bore would increase the chance to prolong the multi-wells gas reservoir production life. Previous experiences of dry gas injection were obtained in the mature gas condensate reservoir belonging to the Rapid River and Cold Spring Fields (located in Canada) via injecting pressurized dry gas which leads to an increase of the surface liquid production from 5 to 15 STB/MMSCF. A similar test was made on 12 reservoirs belonging to Cold Spring Field which also leads to an increase of the surface liquid production from 8 to 10 STB/MMSCF, meaning an increase of surface liquid production of almost 25%.

Venezuelan reservoir fluids under this study have shown concentrations of 2% to 4% of H2S and 10% to 25% of CO2. Initial Production tests combined with PVT data have shown a progressive degradation in hydrocarbon fluid properties with depth and have also shown a sharp decrease of hydrocarbon gravity from 50° to 32° API. The fluid profile showed a noticeable variation from the shallowest reservoirs, with mainly gas condensate fluids, to the deepest ones with mainly volatile types of fluids. The producing GOR of the gas condensate reservoirs ranges from 5000 to 16000 Scf/STB, whereas those for volatile oils range from 2000 to 5000 Scf/STB. Some gas condensate reservoirs have C7+ mole percentages of less than 12.5.

The lab swelling experiments using commercial simulator and field experiences in Latin America have permitted to prove that the injection of dry gas will yield a modification of the reservoir fluid composition as well as its phase envelope, which would increase at the same time the cumulative production, the recovery factor and the production life of the reservoirs.

This content is only available via PDF.
You can access this article if you purchase or spend a download.