One of the most promising targets for resource rock stimulation in South America is the Vaca Muerta (VM) shale in western Argentina. Because of high initial costs and also the typical reservoir information that must be acquired, it is common practice for operators to begin exploration projects with vertical wells. This is also the case for unconventional reservoirs, so initial vertical wells are used for reservoir characterization/initial comprehension and also to test the productivity of the different intervals.Within the Neuquina basin, existing vertical wells were typically drilled to produce reservoirs below the VM source rock. Presently, with these reservoirs depleted in many areas, existing wells are often a great opportunity to investigate this upper unconventional target. Unfortunately, most of these wells are not viable candidates because they were designed to be completed through tubing. Casings and wellheads, in general, are not sufficiently strong to support pressure requirements for fracture stimulation of unconventional reservoirs. This paper discusses the preparation of a well originally drilled in 1974 to allow for the new objective of hydraulic fracturing the VM shale to test the productivity of its different intervals. A coiled tubing (CT) assisted pinpoint completion technique (hydrajet perforating and annulus fracturing) was used to independently stimulate small intervals. To help assure that most of the reservoir was indeed stimulated, 12 single-zone fracturing stages were used for 130 meters of gross interval.To isolate the upper (weakest) section of the wellbore, a 4 1/2-in. P-110 casing and swellable packer were installed.

Many fields in Argentina have multilayer reservoirs that require various stimulation techniques, primarily hydraulic fracturing. A variety of formations and types of reservoirs, such as conventional (mature fields) and unconventional (tight gas and shale), are the main focus in the Golfo San Jorge and Neuquén basin. The hydraulic fractures created in these basins present a variety of conditions and challenges related to depth, well architecture design, bottomhole temperature (BHT), reservoir pressure, and formation permeability. In 2006, a pinpoint completion technique was introduced to help achieve greater efficiency and reduce time and costs associated with completions. This paper presents experiences gained using this technology and proving such versatility in different types of reservoirs. The pinpoint technique, called hydrajet perforating annular-path treatment placement and proppant plugs for diversion (HPAP-PPD), was applied in new wells at different reservoir conditions. The history and evolution of this technique in Argentina was initiated in conventional oil reservoirs (mature fields in Golfo San Jorge) and then was introduced in the Neuquén basin in gas well completions. Throughout the last seven years, this technique has been tested and implemented in tight gas wells. More recently, it was used to improve a completion technique in a shale oil well. This completion method allowed operators to focus treatments in desired zones using specific treatment designs based on reservoir characteristics. Several case histories are presented for different basins, formations, and reservoirs types, highlighting lessons learned and reduced completion time.