The Santa Barbara Field was discovered in 1988 and is one of the largest hydrocarbon accumulations along the Northern Monagas trend, Eastern Venezuela. The producing formations range from Cretaceous to Miocene age, and the area is structurally complex. For about forty percent of the area, a very abrasive, hard to drill, allochthonous wedge of early to late Cretaceous age, which gradually thickens to the north, has to be penetrated to reach the producing formations, increasing exploitation costs. The field is currently producing light oil and condensates at depths between 13,500 and 18,000 feet. The average temperature of the reservoirs is around 290°F and reservoir pressures range between 8,000 and 11500 psi, depending on relative depletion. Asphaltenes precipitation and sand production are some of the operational problems encountered. Furthermore, parts of the field lays underneath a few towns and villages that constrain a regular drainage with vertical wells. A project to inject 1,200 million cubic feet of gas to maintain reservoir pressure is under way. To minimize production problems, to maximize productivity and injectivity, and to improve profitability of the field, a multidisciplinary task force was formed to plan and design highly deviated wells. In this work, reservoir geology and petrophysics, geomechanical characteristics, reservoir simulation, wellbore stability, construction angle rates, drilling hydraulics and drillstring performance design are discussed. To minimize costs, rig capacity was limited to available equipment. A 75° high-angle well is currently being drilled underneath the El Tejero town to reach previously underdeveloped zones, and the preliminary results of the pilot well will be presented. Total measured depth will be 20,240 feet with a vertical section of 5,500 feet. Simulation results for this design show substantial increase in oil production over a vertical well in the target location using a monobore completion. The designs of a high-angle, gas-injector well and a deep multilateral in the allochthonous region are also discussed. The overall recovery factor of the field may well be increased if oil otherwise left behind in low permeability zones is penetrated by highly deviated wells.
Introduction
The Santa Barbara field is located about 25 Km west of Maturin, the capital of the Monagas State in Eastern Venezuela. It forms, along the Orocual, Boqueron, El Furrial, Carito and Carito Oeste fields, a trend of mostly deep giant hydrocarbon accumulations known as the Northern Monagas Area. Actual production along this trend surpasses one million barrels of oil and 2,500 million cubic feet of gas per day, from both natural depletion and water and gas injection projects. The Santa Barbara field was discovered in October 1988, and actually produces about 250,000 barrels of oil and 1,600 cubic feet of gas per day. A project to inject 1,200 million cubic feet of gas is underway to start operations in March 2001 to maintain reservoir pressure.
