A New Method for Compatibility Evaluation of Invisible Acid Workover Fluid and Formation Water

Abstract

The invention relates to a novel method suitable for compatibility evaluation of recessive acid workover fluid and formation water, and belongs to the technical field of oil and gas reservoir development and well workover. The novel method comprises the following six steps that reservoir rock sample powder is added in a triangular flask with a stopper containing an original mixed solution according to the acid fluid proportion of 1.0 g / 20 ml; the triangular flask with the stopper is placed at the constant temperature of the reservoir temperature for 24 hours; experimental phenomena in different periods are observed; the triangular flask with the stopper is taken out to be filtered, dried and weighed; the filter residue mass (m2-m1) is calculated; and the sizes of the masses m0 of the filter residue and the reservoir rock sample powder are compared, if (m2-m1) is greater than m0, meanwhile forming of acicular crystals is obviously observed, it can be ensured that incompatibility existsin the recessive acid workover fluid and the formation water, and otherwise the recessive acid workover fluid and the formation water have good caompatibility. According to the novel method suitable for compatibility evaluation of the recessive acid workover fluid and the formation water, the applicability is high, the reservoir conditions are simulated truly and accurately, compatibility evaluation is completed at the reservoir temperature and the simulated reservoir lithology, quantitative analysis is conducted, and the accuracy of compatibility evaluation is improved. The problems that an existing turbidity evaluation method cannot accurately simulate the reservoir conditions, cannot conduct quantitative analysis, and cannot make a correct assessment are solved.

Description

technical field [0001] The invention relates to a new method for evaluating the compatibility of invisible acid workover fluid and formation water, which belongs to the technical field of oil and gas reservoir development and well workover and production increase. Background technique [0002] When the oil layer is drilled, the drilling fluid filtrate, cement slurry filtrate (including lead slurry) and completion fluid filtrate will inevitably enter the oil layer under the action of pressure difference. Precipitation will cause damage to the oil layer. Invisible acid completion fluid has obvious effects on protecting reservoirs and increasing oil well production, increasing oil well production by more than 10-30% on average. Since stealth acid is better used as completion fluid on site, in order to maintain the oil and gas wells in the best production condition in the middle and late stage of oil and gas field development, stealth acid completion fluid is used as workover f...

AI Technical Summary

Problems solved by technology

The reason is that there is a deviation in the compatibility between invisible acid workover fluid and formation water, and the existing evaluation method for the compatibility of invisible acid workover fluid and formation water still uses the compatibility evaluation method of invisible acid completion fluid and formation water— - Turbidity method, this method has the following defects: one, it cannot detect the impact of the scale-forming ions produced by the invisible acid chelating agent HTA dissolution reservoir minerals on the compatibility of invisible acid workover fluid and formation water under reservoir conditions; Second, the workover operation takes a long time, and the conclusion is inaccurate when placed under the reservoir temperature for a short period of time to observe whether there is sediment formation; third, only qualitative analysis can be performed to observe the formation of sediment and measure the turbidity value, but quantitative analysis is not possible

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