In their effort to continuously improve operations through the development of new and innovative technology, East Mexico operators have focused on optimizing operating times and reducing costs during the completion process by conducting in-situ characterization of gas fields. The challenges encountered when attempting to perform such tests are generally associated with the characteristics of the well completion, the length of open hole (OH) section below the shoe, the type of mud used and the high deviation profile.
These issues have prompted the design of an alternative coiled tubing (CT) conveyed technique. This paper presents the experience of the first deployment of a modular formation dynamics tester (MDT) on CT. This was used to perform several "point pressure tests" and achieve formation characterization of a gas well in the Lizamba Field, State of Veracruz, Mexico. With this new application, the operator was able to significantly reduce time and costs by performing the characterization survey following a conventional CT logging (CTL) operation.
The success of this technique has led to the enhancement of general OH CTL operations by the use of well control equipment at surface to provide formation characterization at slightly over-balance conditions. The greatest challenge is to have effective risk-mitigation procedures to avoid pipe sticking from differential pressure or problems with the small annular clearance between the tool and the wellbore. It has also been extremely important to have an effective contingency plan prepared to recover the toolstring if the stuck-pipe situation does arise.
This paper provides a discussion and analysis of these issues with reference to recent experience with CT-conveyed wireline tools in open hole.
The production of hydrocarbons in the Tertiary Veracruz basin dates back to 1956. However, the area has been reactivated in the last five years with the exploitation of the main gas fields: Cocuite (104 bcf), Novillero (76 bcf) and Veinte (16 bcf). Recently, new fields have been found and developed in a very short cycle; Playuela, Lizamba, Apertura, Vistoso. For example, the Vistoso field made production in less than one year following the 3D seismic processing. The dry gas reservoirs are located in terrigenous rocks that were deposited as slope and basin floor fans, submarine channels (both straight and meandering) and debris flows near the slope of the western part of the Cordoba Basin. The producing stratigraphic units are horizons belonging to the Miocene, Oligocene and Lower Pliocene.
With the acquisition of 3,300 km2 of 3D seismic survey, the success rate increased in the characterization of the geological models and their extension was outlined through the interpretation of seismic attributes considered as gas detectors. The production of dry gas has increased from 38 MMscf in the year 2000 to 525 MMscf in 2005 and is expected to reach 900 MMscf in 2008.
The Lizamba Field in particular comprises a series of gas bearing sand sequences from different stratigraphic levels that can be observed from seismic anomalies, named: Gandara, Lizamba, Cavalieri, Laplace and Napier. The recent development of that field has been optimized by high angle infill wells drilled from macro platforms. The main goal and advantage of such drilling method has been to minimize the ecological impact in an area of lagoons and tropical forest. In addition, increasing the sand thickness exposed (thus increasing the productivity of each well) and reducing installation costs derived from optimizing production facilities have been major drivers. See Figure 1.