An Investigative Study of Potential Emulsion Problems Before Field Development
- Sunil Lalchand Kokal (Saudi Aramco) | Abdullah Al-Ghamdi (Saudi Aramco) | N.S. Meeranpillai (Saudi Aramco)
- Document ID
- Society of Petroleum Engineers
- SPE Projects, Facilities & Construction
- Publication Date
- March 2007
- Document Type
- Journal Paper
- 1 - 10
- 2007. Society of Petroleum Engineers
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Before the development of a field, it is worthwhile to determine the characteristics of crude-oil emulsions. This may be even more important if the wells are to be equipped with electrical-submersible pumps (ESPs) which can create a shearing environment resulting in tight emulsions. One such study was conducted to determine the characteristics of emulsions from a cluster of oil fields planned for development. The proposed development is to produce from three fields and several different reservoirs. The central processing facility (CPF) will process ˜500,000 B/D oil and 50,000 B/D of water. Previous studies determine the impact of ESP on emulsions and on the ESP design (horsepower) and the possibility of demulsifier injection downhole. The emulsion properties are also necessary for the design of central wet crude handling facilities. A series of emulsion tests was conducted with crudes from different reservoirs at bottomhole and surface temperatures, range of water cuts, and shearing conditions. The results are provided in terms of "relative?? tightness of emulsions from different reservoirs. The viscosities of various emulsions were also determined. The results indicate that demulsifier injection facilities will be needed at the wet crude handling facilities and possibly in wells from one reservoir that has a high asphaltenic and viscous crude. This paper provides a framework of laboratory emulsions studies that can provide valuable information for the design of CPFs before they are built. This paper also discusses some practical aspects of demulsifier treatment programs, including demulsifier selection and optimization and methods to prevent emulsion problems.
An important aspect during oilfield development is the design and operation of wet crude handling facilities. The crude oil is partially stabilized (separation of associated gas) and separated from the produced water. The characteristics of the oil/water mixture are important during the separation process. The produced water must be separated from the oil, treated, and disposed properly. The sellable crude oil also must comply with certain product specifications including the amount of basic sediment and water (BS&W) and salt.
The incoming oil/water mixture may be loose and the water may separate easily, or it may be produced in the form of an emulsion. A regular oilfield emulsion is a dispersion of water droplets in oil. Emulsions can be difficult to treat and may cause several operational challenges in wet crude handling facilities and gas/oil separating plants (GOSP). A typical GOSP is shown in Fig. 1. Emulsions can create high-pressure drops in flowlines, lead to an increase in demulsifier use, and sometimes cause trips or upsets in wet crude handling facilities. The problem is usually at its worst during the winter because of lower surface temperatures. The emulsions must be treatedto remove the dispersed water and associated inorganic salts to meet crude specifications for transportation, storage, and export and to reduce corrosion and catalyst poisoning in downstream-processing facilities.
"Crude-oil emulsions?? is a broad area, and several books have been written on the subject. For in-depth details and further reading on the subject matter, the reader is directed to the textbooks (Schramm 1992; Sjoblom 2000)1-2 and website addresses (Sjoblom, Kilpatrick, Masliyah, Wasan, Yarranton) provided in the references.
For the design of a GOSP in a new field, it is important to understand the type of emulsion it will handle and to measure its characteristics. How is the field demulsifier treatment program designed? What kind of demulsifier will be suitable, and what kind of facilities should be included in the design package? This paper provides an example for one such study that was conducted to determine the characteristics of emulsions from a cluster of oilfields planned for development. It also discusses some practical aspects of demulsifier treatment programs that should be useful for the practicing engineer dealing with emulsions, either regularly or on a limited basis. A field emulsion treatment program is discussed and, more importantly, methods to prevent emulsion problems are highlighted. Finally, practical aspects of demulsifier selection and optimization are included.
The focus of the study was to characterize the emulsions from the new fields in terms of their relative tightness. This particular field development consisted of three oil fields that were to be developed together and the crude processed in a CPF (Fig.1). Each field will produce from several different reservoirs. The properties of these crudes are provided in Table 1.
Crude oil samples were collected from Field A (Arab-A, B, C, Hanifa and Hadriya reservoirs), Field B (Arab-D and Fadhili reservoirs) and Field C (Arab-A, B, C, and D reservoirs). None of the fields is on production at present and the oil samples were collected from shut-in wells at the wellhead. Some of the samples did not contain any water and the emulsions were simulated with water collected from the same reservoirs in nearby fields.
|File Size||2 MB||Number of Pages||10|
Kilpatrick, P. (petroleum emulsions,asphaltenes and foams): http://www.che.ncsu.edu/kilpatrick.
Kokal, S.L. 2002. Crude Oil Emulsions:AState-of-the-Art Review. Paper SPE 77497 presented at the SPE AnnualTechnical Conference and Exhibition, San Antonio, Texas, 29 September-2October. DOI:http://www.spe.org/elibrary/servlet/spepreview?id=77497-MS.
Kokal, S.L. 2006. Crude Oil Emulsions.Chapter in the SPE Petroleum Engineering Handbook. Richardson, Texas:Society of Petroleum Engineers.
Kokal, S.L. and Al-Ghamdi, A.M. 2005. Oil-Water Separation Experience Froma Large Oil Field. Paper SPE 93386 presented at the SPE Middle East Oil andGas Show, Kingdom of Bahrain, 12-15 March.DOI:http://www.spe.org/elibrary/servlet/spepreview?id=93386-MS.
Kokal, S.L. and Al-Juraid, J.I. 1998. Reducing Emulsion Problems byControlling Asphaltene Solubility and Precipitation. Paper SPE 48995presented at the SPE Annual Technical Conference and Exhibition, New Orleans,27-30 September. DOI:http://www.spe.org/elibrary/servlet/spepreview?id=48995-MS.
Kokal, S.L. and Al-Juraid, J.I. 1999. Quantification of Various FactorsAffecting Emulsion Stability: Watercut, Temperature, Shear, Asphaltene Content,Demulsifier Dosage and Mixing Different Crudes. SPE paper 56641 presentedat the SPE Annual Technical Conference and Exhibition, Houston, 3-6October. DOI:http://www.spe.org/elibrary/servlet/spepreview?id=56641-MS.
Kokal, S.L. and Alvarez, C.F. 2003. Reducing Pressure Drop in OffshorePipelines by Controlling the Viscosities of Pressurized Emulsions. PaperSPE 81511 presented at the SPE Middle East Oil Show, Kingdom of Bahrain, 9-12June. DOI:http://www.spe.org/elibrary/servlet/spepreview?id=81511-MS.
Kokal, S.L. and Wingrove, M. 2000. Emulsion Separation Index: FromLaboratory to Field Case Studies. Paper SPE 63165 presented at the SPEAnnual Technical Conference and Exhibition, Dallas, 1-4 October.DOI:http://www.spe.org/elibrary/servlet/spepreview?id=63165-MS.
Masliyah, J. (heavy oil and bitumenemulsions): http://www.ualberta.ca/~masliyah/index.htm.
Schramm, L.L. ed. 1992. Emulsions:Fundamentals and Applications in the Petroleum Industry, Adv. Chem. Ser.[Monograph] Series, Washington D.C. Am. Chem. Soc. 231.
Sjoblom, J. (surface/colloid chemistry ofemulsions): http://www.chemeng.ntnu.no/research/polymer/ugelstadlab/publpat.htm#publications.
Wasan, D.T. (interfacial rheology,emulsions): http://www.iit.edu/dept/che/grad/faculty/wasan.html.
Yarranton, H. (asphaltenes and emulsionstability): http://www.eng.ucalgary.ca/resrch_chem/Chem_Yarranton.htm.