Society of Petroleum Engineers
Distinguished Lecturer 2003-04 Lecture Season
Downhole Water Separation
Andrew K. Wojtanowicz
During the economic life of a producing field, the volume of produced water may exceed the volume of hydrocarbon produced by 10 times. During late stages of production, it is not uncommon to find that produced water can account for as much as 98% of the extracted fluids. Historically, the average worldwide water cut is 75%, while the average water handling Opex cost to the oil industry is $0.50 per barrel of water, amounting to $40 billion total.
Since the conventional process of fluid separation is energy intensive and very costly, the industry has searched for innovative techniques that would move the separation upstream the production process, i.e. to the wells bottom, or even back to the reservoir.
The presentation will introduce modern technologies for separation of water in oil and gas wells. In principle, these techniques fall into one of two categories: bottomhole separation and separation in situ. The bottomhole separation techniques utilize separation inside the well. Discussion will include bottomhole systems based on gravity separation of gas and water (modified plunger, bypass tool, ESP) and gravity separation of oil and waterdual/triple action pumping (DAPS/TAPS), hydraulic submersible pump (HSP), and horizontal gravity separator (HSep). The discussion will include field performance and several case histories, since some of these systems have been successfully commercialized.
Also presented will be the downhole oil water separation (DHOWS) technology using bottomhole mechanical separatorshydro cyclones with or without ESP. The presentation will discuss downhole installation and completion aspects of these techniques as well as the limitations of hydro cyclones as separation devices. Several case histories of DHOWS demonstration projects will be also presented.
The final part of the presentation will concern a dual-completion technology using in-situ separation of water from oil or gas in the reservoir outside a producing well (downhole-water-sink technology, or DWS). In DWS wells, the second (bottom) completion is used for draining water in order to maintain the wells potential for production of oil/gas from the top completion. Explained will be principles of DWS well performance in the bottom water and edge water reservoirs. A case history will show details of downhole installation and production data. Also discussed will be the comparison of DWS with conventional wells and incremental recovery due to the technology.
Andrew K. Wojtanowicz is Texaco-endowed Environmental Chair in Petroleum Engineering at Louisiana State U. and U.N. expert in drilling engineering. He has worked in the petroleum industry as a drilling engineer, drilling supervisor, and drilling fluids technologist in Europe and Africa. Wojtanowicz has held faculty positions at three universities and conducted research in drilling, completion, and production operations with emphasis on environmental effects and prevention techniques. His studies are reported in 180 publications and four books. He is an Editor-in-Chief of ASME Transactions Journal of Energy Resources Technology and a registered petroleum and environmental engineer in Louisiana. As a Conoco Environmental Research Fellow 91/92, he developed dewatering technology for closed-loop drilling systems. He has also developed water coning-control technique with Downhole Water Sink (DWS) well completion, for which he received Special Meritorious Award for Engineering Innovation in 1996. He has directed a DWS Joint Industry Project at LSU since 1997.
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