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A geostatistical study has been performed in the framework of the Integrated Reservoir Study of the giant Bachaquero 2 oil field, located in the Maracaibo lake, Venezuela. The objective of the study was to take advantage of the exceptional well density (over 1300 wells) in order to build a detailed and robust 3D model for geological risk evaluation during drilling, as well as further reservoir modelling studies. The geostatistical database has been built from the preliminary deterministic geological work (3D seismic interpretation, sequence stratigraphy, sedimentological and petrophysical analysis). Stochastic simulations have been run in terms of facies and petrophysical properties, using a pixel based, Truncated-Gaussian algorithm. The stochastic model has been used in a variety of applications, from optimization of horizontal well trajectories, to infill drilling location and the construction of local scale numerical simulation models.

A large scale integrated study has been performed in the Bachaquero Intercampos Field, Lake Maracaibo, Venezuela. The project concentrated on the complete revision of the static and dynamic models of the field, with the aim of identifying new reserves and define a new development plan. The dimension of the field and the huge amount of available data required an effort in terms of prioritizing the technological and human resources allocated to each discipline. The new geological model revealed the presence of a previously untargeted shadow zone below the main reverse fault of the field (subthrust trap). The development plan was focussed on the exploitation of these new reserves and is adding about 10 years of production to the field. The first phase of the development plan started in early 1998 and so far 3 wells have been drilled and completed. These wells confirmed the new geological model and are currently producing more than 15% of the total field production.

Abstract Recent development of Bachaquero 2 Field (Lake Maracaibo, Venezuela) has been based mainly on cyclic steam injection on horizontal wells. Initial oil deliverability of the heated wells proved to be up to 5 times greater with respect to the cold wells. This paper presents the results of a multi-disciplinary project focussed on the drilling of a pair of horizontal wells for cyclic stearn injection. The project involved a reservoir characterization and a numerical simulation phase, the drilling, steam injection and production of these wells, a data acquisition project and eventually a fial detailed simulation stage. Experimental and numerical results show that the presence and the thickness of interbedded shale has a severe impact on heat distribution. Very little interference has to be expected between parallel horizontal wells when the separating shale is continuous and its average thickness is greater than about 12 feet. A preliminary stochastic description of the reservoir can be very useful in assessing the presence and expected average thickness of the interbedded shale. The experience allowed us to set the best production strategy for the 2-horizontal well system, in terms of sequence and duration of the cycles, steam rate, total injected steam, steam quality and soak time. It also helped in setting guidelines for the future development of the Bachaquero 2 Field. P. 293