RIASSUNTO
Abstract
Tropical wetlands and the presence of indigenous people with an ancient culture and strong economic dependence on natural resources, made the Pedernales field an environmental and social sensitive location. The challenge for BPA was to operate in this area without disrupting the lifestyle of the nearby settlements while preserving the environment.
Pedernales field was designed as a zero discharge operation, where the main was streams were to be re-injected. However, due to operational constraints, the initial waste management strategy had to be changed to one that also allowed the disposal of wastes in an environmentally sound way. Waste recycling, bio-treatment and temporary off site treatment and disposal were the key processes of the new waste management strategy.
During 5 years of operations, a total of approximately 2.6 MM bbl of E&P waste were handled and disposed successfully. Poor area drainage, combined with high annual rainfall and low natural soil supporting capacity, required the use of non-conventional tools and equipment; this was more evident for the disposal of drilling cuttings.
Drilling cuttings were handled by turning them into slurry using a specially designed mixer, and then pumping the slurry to a distance of up to 2 Km from the storage barge. Oil degradation from 6%, oil and grease, down to 1% was accomplished in approximately 180 days. This is considered to be a short time taking into account the high level of soil/waste moisture saturation. Continuous monitoring of water and soil with a simple on-site laboratory proved to be adequate and cost effective for process control and prevent environmental pollution.
Background
Pedernales field was granted to BP Venezuela in the framework of the reactivation policy of marginal fields of PDVSA in 1994. This field is located on the Northeastern part of the country, between coordinates 9 54' - 10 05'N and 63 00' 620'W and has an approximate area of 48,000 Ha. The drilling and production facilities are located on the mouth of Caño Pedernales, one of the main branches where the Orinoco River drains its water into the Atlantic Ocean. During from 1995 to 1997, 44 wells were drilled, all directional with an average MD of 12,000 feet. In order to minimize the visual and environmental impact, drilling platforms were designed to contain cluster of up to 25 wells. The production facilities are divided into 3 clusters of wells platforms and 2 crude flow stations, both built on floating barges. Produced crude oil was stored in a marine barge, and then shipped to exportation destination.
Environment
The water flow of the river is completely dominated by the influx and reflux of the tides, giving the water the features of estuarine environment, river water chlorides content range from 4000 to 12000 mg/l, depending on season and influx or out flux of the tide. The river banks vegetation consist of mangroves, mainly red mangrove (Rhisophora mangle) and black mangrove (Avicennia germinans), which reach a height up to 30 m, forming a dense coastal forest. These trees are the basis to the sediments fixation and soil formation and at the same time they serve as shelters for a great number of birds. Additionally, the surroundings of the roots allow the embryonic development of fish and crustaceans such as shrimps. In the river banks, at approximately 3 km from the production platforms, are the villages of Capure and Pedernales, which population is partially indigenous. Some individuals of this population, with a adequate training, was part of the labor used in the operations.