Improved Transportation of Waxy Crude Oils and Emulsions in Bekasap Area, Indonesia
- Y. Tang (California Institute of Technology) | P.J. Shuler (California Institute of Technology) | S.K. Cheug (ChevronTexaco Corp.) | J.A. Goodgame (ChevronTexaco Corp.) | J.J. Hsu (ChevronTexaco Corp.) | A.V. Padilla (ChevronTexaco Corp.)
- Document ID
- Society of Petroleum Engineers
- International Symposium on Oilfield Chemistry, 5-7 February, Houston, Texas
- Publication Date
- Document Type
- Conference Paper
- 2003. Society of Petroleum Engineers
- 4.2 Pipelines, Flowlines and Risers, 5.4.6 Thermal Methods, 3 Production and Well Operations, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 4.1.5 Processing Equipment, 5.5.1 Simulator Development, 4.1.2 Separation and Treating
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One challenge in the production of oil fields in the remote Bekasap Area of Indonesia is the transportation of waxy crude oils through long pipelines. The current practice is to add hot water to the oil so fluids remain well above the pour point temperature of the crude (90 - 105 °F). This, however, limits oil-carrying capacity and increases costs due to handling and separating oil/water mixtures. This study focused on understanding the causes of the high pipeline pressures and to develop more economic transportation strategies. Laboratory measurements included oil/water emulsion rheology over a wide span of conditions, wax/gel formation, and the effect of various chemical treatment additives. A customized spreadsheet program was developed to model the current pipeline operation and to predict the change in pipeline pressures/temperatures under different scenarios.
The results indicate that the formation of relatively high viscosity oil/water emulsions is the most likely cause for the high pressure losses in these flowlines. Laboratory measurements demonstrate these oil/water mixtures have a complex physical nature and rheology. Simulations indicate the potential benefit of reducing the mixture viscosities via chemical treatment or heat management. For the Pinang Field, which was studied in the most detail, adding insulation to bare pipe areas provided a successful solution.
The Bekasap Area is one of the important oil production regions in the Riau Province of Central Sumatra, Indonesia. The fields in this area typically produce waxy, high pour point oils.
Because the pour point is high (90 - 110 °F) for these waxy oils, and can even exceed ambient temperatures in Sumatra, the (untreated) oil temperature is increased in order to allow the oil to flow in the pipeline. Hot water/steam addition to the crude oil has been used to provide this required heat. This approach is convenient as it is a relatively simple operation to lift hot water from old production wells that no longer produce oil, and plumb this water into the oil export line. For example, at Pinang Field (Figure 1) hot water is added at 3 different points near the start of the line, supplemented by steam injection towards the end of the pipeline. This general design is typical of other Bekasap Area flowlines that transport waxy crude oil from remote fields to a central processing station. This study focused on the Pinang line in particular as it has been limited in its ability to deliver the target rate of crude oil. In addition, there was a suite of operational experience and data available for the Pinang line.
This practice of adding hot water has some advantages: 1) it is easy to implement in this remote location, 2) this source of heat is readily available, and 3) has a relatively low cost. However, there are several reasons to seek improved strategies to transport the waxy crudes in the Bekasap area:
line capacity to deliver oil is less than the target rate, especially when anticipating future field expansion
the volume of added hot water greatly exceeds the volume of oil transported. Decreasing the water rate would reduce the costs to lift the water and separate the oil/water mixture at the end of the flowline.
pressure losses have been higher than expected, thus increasing the pumping costs; this is a particular problem in cool and rainy weather
there are several fields that have similar problems with transporting high pour point oils. Lessons learned in the Pinang study should apply elsewhere.
Treatment Options and Preliminary Analysis
One option explored previously was chemical treatment of the oil so as to avoid any requirement for adding hot water. Experimental results indicated that by adding a combination of a lighter hydrocarbon diluent and a pour point depressant it was technically possible to reduce the pour point of the Pinang crude oil significantly. There are field cases in the literature where this approach has been employed successfully.1,2 However, the chemical treatment cost required to reduce the pour point enough to guarantee successful transport of the crude oil appeared to be uneconomic. This current study strives instead to improve the hot water addition approach.
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