Integrated Multidiscipline Approach Lead To A Recent Success In Naturally Fractured Reservoir - The Macueta Experience.

Abstract

The Macueta is a gas field located in the Acambuco Area, Tarija Basin, Northwest Argentina. This area is owned by the Acambuco Consortium: Pan American Energy (operator, 52%), Shell (22.5%), Repsol-YPF (22.5%), Apco (1.5%) and NorthWest (1.5%). The reservoir is formed by tight naturally fractured quarzitic sandstones of Devonian age (Huamampampa and Icla Formations), trapped in a narrow and elongated anticline within the subandean region. Since the early 80's, four drilling initiatives, including vertical and horizontal wells, showed moderate to no success at all (AOF = 3 MMscfd − 14 MMscfd). A new approach, using modern well testing and logging tools, was performed. This approach, including a careful study of the fracture system, in situ stress analysis and fracture production characterization, turned the view and triggered the field development. The key to success was the identification, through selective zone well testing, of a zone far from the wellbore with high permeability, and its association with better fracture development in the crestal zone of the structure. This finding helped to understand the production mechanism of the reservoir. This study is supported by acoustic image logs, production logs and well tests taken in Mac.x-1001bis, a former vertical well. In this well, a succesful drilling reentry operation was executed after planning a 1150 ft long horizontal well trajectory with improved chances of success by maximizing fracture intersection. The Mac.x-1001bis reentry well tested 36 MMscfd of gas and it has an absolute open flow (AOF) of 144 MMscfd. This increase of productivity, up to 40 times compared with the former wells, proves the convenience of horizontal technology in naturally fractured environments when it is carefully planned and executed. This well sets a record in the basin for the Icla Fm. and opens new expectations and possibilities for the development of this type of reservoirs. Introduction A highly successful experience which relates horizontal drilling, effective fracture identification and production deliverability is reported in a naturally fractured reservoir (NFR). A careful planning and selection among several drilling alternatives is presented. Although the existence of gas was proven since the early 80 s, the productivity per well was low and the field development has been delayed for several years. Table 1 summarizes the results and history of existing wells. The Mac.x-1001 (1982) well discovered the field in Huamampampa Fm. but due to technical reasons, it was abandoned. Mac.x-1002 well (1984) was planned as an offset well and was also abandoned due to the lack of productivity. The Mac.x-1001bis (2000), a twin well of the former Mac.x-1001, reached moderate levels of productivity, and provided new information acquired with modern technology.

Kinematic structural restorations and discrete fracture modeling of a thrust trap: a case study from the Tarija Basin, Argentina

“…the crest where most wells are positioned (based on the inferred fracture -curvature relationship, Masaferro et al, 2003), and low density further on the back limb. Well data from San Pedrito and Macueta Girardi et al, 2002), fit this pattern, with the fracture sets parallel and orthogonal to the fold axis being dominant, although front limb wells are absent. At the moment we cannot rank a curvature or strain based fracture assessment for the Tuyunti field purely based on data, as sufficient coverage of good fracture data over the structure is not available.…”

“…As no well data was available for Tuyunti at the time of this study, we assumed a theoretical fracture network, as is often observed in classical field examples of similar structures (Couples et al, 1998;Price & Cosgrove, 1990) (Fig. 6), which was further justified by well data in nearby similar structures Girardi et al, 2002). It consists of 3 fracture sets, one striking parallel to the main fold axis, one orthogonal to it, and a conjugate set around the latter one.…”

“…Once a good fit is found between model and observations, the technical risk for the fractured reservoir is highly reduced and future well characteristics and performance will be more predictable. For the Tuyunti and nearby structures, the above described approach has helped to define optimum well trajectories and development strategies Girardi et al, 2002), where the front limbs now receive more attention as potential well targets, as well as improve fractured reservoir volume estimations.…”

“…Hydrocarbon generation and migration is coeval with the formation of the structures (Echavarria et al, 2003). Some of these structures, like San Pedrito and Macueta, Girardi et al, 2002), are successful gas producers, while exploration and development of other fields like Tuyunti is ongoing (Kozlowski, La Motta, Porcelli, Cohen, & Sylwan, 2001).…”

“…In our case, strain maps are used as input attribute map to control fracture density. Orientation of the fracture sets comes from the generalized regional observations on fractures (Antonellini, 1998;Girardi et al, 2002). The length of the fractures is arbitrary and is set equal for all fractures unless otherwise stated.…”