The condensation point refers to the highest temperature at which the sample cools under specified conditions until the liquid level stops moving.The determination of condensation point is of great significance in oil pipeline transportation. Using an automatic ice/tilt/pour point analyzer to analyze the condensation point can provide technical basis for oil pipeline transportation, reduce transportation costs, and improve production efficiency.

The Significance of Measuring the Condensation Point of Crude Oil

The composition of crude oil is complex, with wax components above carbon-16 easily crystallizing and precipitating at low temperatures, gradually forming a wax crystal network as the temperature decreases, causing the crude oil to gradually lose its fluidity. Condensation point,as an important indicator for evaluating the low-temperature fluidity of crude oil, the accuracy of its test results directly affects the production and operation management of petroleum products. On the one hand, it is an important basis for the design of crude oil pipelines; On the other hand, it also has significant guiding value for the use, storage, and transportation of petroleum products.

In addition, there is a common phenomenon of low throughput operation in crude oil pipelines both domestically and internationally. Currently, most of these low throughput pipelines have adopted measures such as using pour point depressants or drag reducers.So, in order to further ensure the orderly development of oil pipeline engineering and reduce the possibility of crude oil coagulation after pipeline shutdown, we need to accurately measure the condensation point of modified crude oil to ensure the safety of pipeline shutdown.

Determination Method for Condensation Point of Crude Oil

At present, the testing methods for crude oil condensation point in China are mainly based on GB/T 510 (national standard method) and SY/T 0541 (industry standard method).GB/T 510 specifies the testing method: place the sample in a specified test tube, cool it to the expected temperature, tilt the test tube at a 45ºangle to the horizontal and let it stand for 1 minute, observe whether the liquid level moves, and use the highest temperature when the liquid level does not move as the freezing point of the sample; The cooling method adopts the cooling bath mode, and the temperature of the cooling bath is 7-8℃ lower than the expected condensation point.

The national standard method is well suited for determining the condensation point of various petroleum products, but it is not yet mature enough for determining the condensation point of increasingly complex crude oils, especially multi wax crude oils that are sensitive to heat treatment.The national standard method is not clear enough about the preheating of samples, the room temperature requirements are not specific enough, and the dehydration treatment conditions are not suitable for crude oil; In addition, repeated heating during the measurement can also alter the flow characteristics of crude oil, which can lead to certain deviations in the results.

SY/T 0541 involves loading a preheated oil sample into a test tube and cooling the sample at a cooling rate of 0.5~1℃/min until it reaches a temperature 8℃ higher than the expected condensation point. Then, the flowability of the sample is observed every 2℃ decrease until the test tube is horizontally placed for 5 seconds and the sample does not flow. The highest temperature in this state is the condensation point.

The industry standard method has standardized requirements for preheating oil samples, avoiding reheating; At the same time, a step-by-step cooling method was adopted, and there were clear regulations on the cooling rate.However, this method still has some drawbacks, as there may be fog obstructing the view when removing the test tube from the sleeve to observe the flow of the sample; Moreover, after removal, it is highly susceptible to heat, which can damage the crystallization of the tube wall. Excessive tilting can also affect samples with weak wax mesh structures.

The pressure pulse method is a convenient and efficient automatic detection method that can be effectively applied to the detection of crude oil condensation point. This method applies a moving force formed by pressurized gas pulses to the surface of the sample at a preset temperature, and uses a set of optical detectors connected to a light source to detect the movement of the sample surface. Compared with the two methods mentioned above, the pressure pulse method has the advantages of small sample size, accuracy, high efficiency, and low pollution.