API RP 87:2007 pdf download

API RP 87:2007 pdf download.Recommended Practice for Field Analysis of Crude Oil Samples
Containing from Two to Fifty Percent Water by Volume.
a) Centrifuge method;
b) Graduated cylinder method:
C) API MPMS Chapter 102/ ASTM D 4006 distillation (reduced sample size).
NOTE This method is deemed as a referee method to be perloimed on shore or in wi estabEshed not a tie) aeoatory.
8.1.2 Test Methods Considered but Retected for Offshore Use
a) Reduced volume (10 mL), API MPMS Chapter 10.2 1 ASTM D 4006 distillation method, was considered for offshore use but eliminated due to the need to gravimethcally measure the sample to a high level of precision. While equipment may improve in the future, it is interred herein that precision weigh scales required for this method can not be effectively used on offshore facilities, However, as stated above, this method has been designated as the onshore referee method.
b) Distillation method (ASTM 0 95) with standard, 200 mL crude oil sample and 20 mL trap with pet cock drain. The tests conducted as a basis for this RP demonstrated that large amounts of water in the sample caused violent boiling problems with subsequent condenser eruption.
C) Preseparation graduated cylinder method of determining water content of the remaining oil phase by distillation (API MPMS 10.2 / ASTM D 4006) or Karl Fischer titration. This method was abandoned due to inherent problems In obtaining a representative aliquot sample from the larger oil phase sample.
d) Reduced sample size centrifuge tests (API MPMS 10.3 / ASTM D 4007) with the intent to increase the resolution through readability of scale (oilwater interface readings in the conical sect.on for better resolution). This method was abandoned since results were better using the volume specified in the standard centrifuge test method.
e) The Karl Fischer (KF) titration method is considered to very precise and may be applicable for high water content samples. However, in this method as the water content increases the iniected KF sample volume must be reduced because of reagent dilution. Therefore, precision weigh scales are required. which do not function well, or at all, when they can not be positioned on a motionless foundation such as is typical on offshore facilities.
8.2 Centrifuge Method
The centrifuge method (API MPMS Chapter 10.3 1 ASTM D 4007) is the most widely accepted laboratory (and field) anatytical method in fiscal applications for several reasons:
— industry test results are well dooumented:
— good precision with minimal bias:
— inclusion of sediment:
— applicable for a wide range of crude oil types (insensitive to color, density. viscosity, sand, corrosition and salinity);
— ease of use:
— speed of results; and,
— relatively low-cost apparatus.
C) Centrifuge tubes should be calrated and verification numbers etched In accordance with 7.1. Corrections to readings should be applied where applicable,
d) Samples should be taken directly into me centrifuge tubes if they can be filled exactly to the 50 mL graduation (i.e. no volume reduction due to foam). It is critical that the total volume be measured precisely for samples with high water content. (For example, at the 50 % water content level a I ml reading error in total volume results in a 1 % error in net oil content.)
e) If foaming prohibits tilling tubes to exactly 50 mL, an alternate method may be used. This method allows:
1) FIlIwig tubes to appmximately 50 mL (without being exactly at 50 ml).
2) Summing the total sample volumes from two or four tubes.
3) Dividing the sum of the water volumes by the sum ol the total volumes. Regardless of the actual total volume amount (i.e. not exactly 50 mL). Equation 1 still applies.
8.2.2 AutomatIc Sampler Centrifuge AnalysIs Procedure
a) Run sample receiver circulating pumpimixer for appropriate time to insure homogeneous mixture and representative aliquot samples.
b) While circulating pump is running, fill two or four centrifuge tubes to exactly 50 mL graduation after the sample has sallied from foaming.
c) Add 2 to 3 drops of dernulsifier per API MPMS Chapter 10.2 / ASTU D 4006 to ensure a definite, dear interlace without emulsion layer.
d) Add 50 mL of water saturated solvent per API MPMS Chapter 10.2/ ASTM D 4006.
e) Stopper, mix by inverting ten times, heat to 140 °F (60 C) and centrifuge per API MPMS Chapter 10.2/ ASTM D 4006.
f) Place tubes in a rack to ensure vertical orientation.
g) Read the interface volume.