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Wax Appearance Temperature (WAT) with a Cold Finger Apparatus: An Previous HitEffectiveNext Hit Reservoir Management Tool

WAVREK, D. A, N. F. DAHDAH, D. K. CURTISS,  M. D. DEO, and C. G. SEAMAN

The quantity and nature of wax deposition is an important consideration in oil field and reservoir management. The term wax includes a variety of parafinic compounds with carbon chain lengths from C[15] to C[80+] that are solubilized in the crude oil by the lower molecular weight fractions. The primary control on solubility is temperature with a lesser influence by pressure. The critical point for the precipitation event is referred to as the wax appearance temperature (WAT).

Cost Previous HiteffectiveTop strategies for managing a wax problem are focused on prevention, but this requires an accurate method of forecasting the WAT. A cold finger apparatus has been constructed to quantify the how much and when of wax deposition, whereas quantitative high temperature gas chromatography (HTGC) and mass spectrometry (HTGC-MS) provide characterization on a molecular level. The apparatus has the advantage over traditional WAT techniques since the critical variables can be tested in various what if senarios. Results indicate that the diverse assemblage of high molecular weight compounds present in virgin crude oil are fractionated during the formation of the wax deposit; an observation that is confirmed in pipeline studies. Also, these studies indicate oil vs. cold finger temperatures can be varied to change the rate and composition of the wax deposit. Thus, this apparatus can be used to evaluate the probability of the wax formation, in conjunction with providing details on the molecular composition.

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.