Radial Drilling in Argentina

Abstract

Abstract With a world context of high oil prices and a rate of increase in reserves from new discoveries, that is not enough to compensate the rate of extraction, in addition to the high maturity of oilfields currently being developed in Argentina, companies have been working to improve the recovery factor of reserves, as a strategy to extend the useful life of the existing assets. Working in this direction, radial drilling technology seems to be an alternative, which, in spite of the fact that it currently raises uncertainty since it has never been tested in the past in or country, can be adapted to the existing wells thus becoming a low investment alternative. The technology involves drilling lateral horizontal bores of small diameter and up to one hundred meters long, with the possibility of placing several within the each productive layer. The laterals are made in two steps: First, the casing is perforated with a ¾" mill and then the lateral extension is carried out by high pressure water jetting. For this evaluation, pilot tests were performed in different oilfields, with the intention of covering a wide range of possible scenarios and being able to evaluate the best applications for this new alternative. The selected scenarios and the different basins are the following: Golfo San Jorge Basin:Mature Oilfields: already exploited formations with production below the economic limit.Viscous Oils: Formations with high viscosity oil and low mobility. Neuquén Basin:Mature Oilfields: low production formationsPrecuyano Formation (altered ignimbrites) of low permeability, with possible micro-fissures to improve net production.Water Injection: To increase secondary recovery improving the sweeping of the formation. This work shows the different experiences undergone by Repsol YPF in Argentina with this technology as well as shares the results obtained and the lessons learned. Introduction It is extremely important to have the possibility of increasing production and raising usable reserves from the known horizons; due to these facts, the search for new technologies to increase production was started, and it was then that the radial drilling technique appeared as a promising one.(Ref 1, 2 and 3) This process consists in making small diameter horizontal perforations by using water jets at high pressure (jetting). The diameter of these lateral horizontal perforations is of approximately 2 inches (5,08 cm) and up to 330 ft (100 m) of extension each, at the same productive level. Each one has a bending radius as small as 1 ft (30 cm) and is made in two steps: first, the casing is perforated with a 0.75-inch mill (19.05 mm), and then the horizontal extension is made with high-pressure fluid jetting (Figs. 1 and 2). This application combines the following important factors:Low cost, it is applied to existing wells (new wells are not required).Low geological uncertainty.Low environmental risk. Among various reasons for this technique to increase production, the following could be highlighted (Ref. 1):Improves the conductivity of an important area around the well (improving drain efficiency).Possibility to define direction of the perforations.Helps the mobilization of viscous oils.Connects to areas of better petrophysical conditions.Allows intervention of oil reservoirs limited by close-by aquifers.