Zero Discharge System: An Innovative Drilling Rig Design to Protect the Environment in Lake Maracaibo
- D. Suarez (PDVSA Petroleum & Gas) | G.J. Segovia (Schlumberger) | R.E. Valera (Schlumberger) | L.A. Nava (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE/IADC Drilling Conference, 19-21 February, Amsterdam, Netherlands
- Publication Date
- Document Type
- Conference Paper
- 2003. SPE/IADC Drilling Conference
- 5.6.1 Open hole/cased hole log analysis, 6.5.3 Waste Management, 4.1.5 Processing Equipment, 4.2 Pipelines, Flowlines and Risers, 1.6 Drilling Operations, 1.10 Drilling Equipment, 1.11 Drilling Fluids and Materials, 2.4.5 Gravel pack design & evaluation, 3 Production and Well Operations, 2.2.2 Perforating, 5.3.4 Integration of geomechanics in models, 1.12.1 Measurement While Drilling, 1.7 Pressure Management, 4.1.2 Separation and Treating, 6.5.5 Oil and Chemical Spills, 1.14 Casing and Cementing
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In 1999 the operator entered into a 10-yr contract with an oilfield services company to drill and work over wells in mature areas of Maracaibo Lake. In this alliance the operator will share risks and involve the services company in the operations performance through an incentive-penalty scheme with the objective of reducing operation times and costs, protecting the environment, maximizing reserves recovery and introducing technologies to achieve the desired goals.
The engineers pooled their knowledge and expertise to build multipurpose green rigs designed for well construction and work over on Lake Maracaibo environment. Likewise, each rig has a sophisticated treatment system to recycle wastewater into water suitable for industrial use. The document presents how this system can avoid pollution and the wastes are sent onshore to be taken to a zone designated for their final disposal or recycling and the sophisticated system that these rigs have to operate with zero discharge of any pollutants in Lake Maracaibo.
In the early '90s, Bolivar Coast fields reservoir pressures decreased considerably due to massive exploitation. At the same time, operations with traditional equipment proved inadequate for current conditions of the wells in this area with large reserves of light crude. To understand this situation more fully, the operator conducted a series of surveys, which indicated the technology necessary to exploit these reserves, estimated at 20 billion barrels, was missing. Among other things, it was considered that drilling should be made with low-density muds, that is, areas where the density of the drilling fluid should be between 6 to 7 ppg, and at the same time go through the productive zone with fluids with a density lower than 2 ppg.
At the beginning the integrated services with the objectives of introducing new technology, reducing operational times and generating profits by increasing the production had unsatisfactory results. High operational costs were incurred for lengthy rig times, and auxiliary units were often needed for services such as well logging, cementing and perforating. In addition, the environment in Lake Maracaibo was so many impacted by pollution from drilling and work over fluid discharged in the lake. Among the problems that impacted rig time were:
Poor weather conditions that prevented service barges from approaching the rig
Delays due to circulation losses
Difficulties in acquiring good well logs
Inadequate lake transportation
Labor union pressures
Thanks to the long-term alliance commitment, an important first step was taken when scientists and engineers pooled their knowledge and expertise to build multipurpose rigs specifically designed for well construction and work over on Lake Maracaibo. Frequently, coiled tubing is used for fishing, but it also plays an important role in sand- and cement-cleaning operations. Finally, a team effort led to the adoption of special fluids, and a zero-discharge technique was put in place to protect the environment in Lake Maracaibo.
Statement of Problem
Lake Maracaibo is the biggest fresh water reservoir in the world (Fig. 1). From the beginning of Venezuelan oil company in 1914, more than 12,000 wells have been drilled in the lake and the pollution has been affecting aquatic environment and reducing green spaces in the area. Although, the oil company has made many efforts to avoid pollutants into Lake Maracaibo, the rig designs available have not permitted to achieve these goals. In addition, the environmental impact has affected significantly oil industry finances, too.
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