Method for reconstructing wax precipitation point of wax-bearing crude oil in stratum

Abstract

The invention discloses a method for reconstructing a wax precipitation point of wax-bearing crude oil in a stratum, the method comprises the following steps: judging the representativeness of ground crude oil according to the macroscopic and microscopic physical property change of the ground crude oil; for ground crude oil without representativeness, compounding a scale sample and a crude oil sample which are collected at present according to the proportion of normal crude oil in a microcrystal backfilling manner, reducing the crude oil sample with complete components, and then obtaining the most real wax precipitation point through a differential scanning calorimetry and numerical simulation. According to the method, the most real wax precipitation point of the crude oil can be obtained, so that whether wax precipitation of the wax-containing crude oil occurs in the pipeline transportation or well lifting process or not and whether the transportation safety is affected or not can be judged more accurately, and economic and effective wax control measures are taken accordingly.

Description

technical field [0001] The invention relates to the technical field of oil reservoir development, in particular to a method for reconstructing the wax precipitation point of waxy crude oil in a formation. Background technique [0002] The waxing point of crude oil is an important parameter for the fluidity of crude oil in the pipeline environment and wellbore lifting. The test of the waxing point of crude oil on the ground has been widely used in oil storage, transportation and production. Whether wax is precipitated during the well lifting process will affect the safety of transportation. Different from surface crude oil, crude oil under formation conditions contains a large amount of dissolved gas, and the heating of light components will affect the wax precipitation point, so the test methods are also different. At present, domestic and foreign studies on the testing methods of waxy point of crude oil are mostly based on ground degassed crude oil (dead oil), and only a f...

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Problems solved by technology

[0006] The rotational viscosity method is to measure and record the shear stress or viscosity-temperature curve of the crude oil sample during the continuous cooling process at a specified shear rate; figure 1 As shown, the viscosity-temperature curve turns at 65°C, which is considered to be the wax precipitation temperature of ground samples; this method is relatively simple, and has two disadvantages: 1) This method is not suitable for slow initial wax precipitation or containing For crude oil with low wax content, too low wax content will have a slow effect on shear stress, making it difficult to identify the wax precipitation point; 2) Some scholars have questioned the continuous cooling method specified in the SY / T0522-2008 standard. ", the temperature of the insulation jacket cannot be transferred to the sample for a short time, which will cause the test viscosity to be too small, and an improved method of reducing the error by adopting a segmented cooling method is proposed;

[0026] Similar to the principle of light wave propagation, the ultrasonic pulse contains multiple frequency components. During the propagation process of a single medium, its main frequency component will attenuate first, and the attenuation is dominated by absorption; and with the precipitation of solid wax crystals from crude oil, The initial single-phase system becomes solid-liquid two-phase, and the attenuation effect of the whole system is enhanced. At this time, if the initial single-phase attenuation coefficient is still assumed to be unchanged, the observed frequency of the first wave will change, and the inflection point can be used to determine the analytical value. wax point; therefore, the waxing point of crude oil can be obtained by drawing the change curve of the main frequency of the sound wave at different temperatures; however, as Figure 7 As shown, the power at the waxing point of live oil is about 60.11°C is extremely weak, and it is impossible to judge whether the waxing is or not

[0027] The above analysis methods of ground crude oil and gas-bearing crude oil have the same problem. For representative samples, the detected data is the real wax point. When the ground sample crude oil lacks some components, the tested data The waxing point may deviate from the true waxing point

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