Abstract
Search to improve reservoir productivity is a constant issue in oil industry. Specifically in well drilling operations, new technologies are continuously developed. As to underbalanced drilling, this technology has become a very advantageous alternative, compared to conventional drilling to increase reservoir productivity, When drilling with a pressure gradient favorable to formation, formation damage risks are considerably diminished, This will allow exploiting a reservoir without drilling too many wells, due to its high productivity. On the other hand, use of this technology in low-production pressurized reservoirs implies that increase of well productivity would greatly compensate investments performed in equipment. This can be achieved, either by adapting low cost equipment (fit for service), or by massively implanting the technology in a reservoir. In this paper both technical and economic aspects that condition underbalanced drilling application as a technology to improve reservoir productivity are entirely analyzed. Proper selection of candidate wells are considered, using a data base and similar wells, to evaluate adaptability of the technology, as well to estimate the increase of production because of the use of the technology in a hypothetical case of an oil reservoir and a real case of a condensate gas reservoir. Also, reference is made to different formation damage mechanisms that will not be necessary to apply if underbalanced drilling is used. Concerning the economic aspect, implication of the production simulator, as well as of the reservoir useful lifetime, on the calculations of the project net present value (NPV) is taken into account, considering application of underbalanced operations both in well drilling and well workover Successful and systematic application of this technology is associated to the need of creating work teams of professionals from all the stages of the production chain value.