| Lost and vicious lost circulation has seriously effected on the oil and gas well exploration and development. At present, the conventional solution of plugging vicious lost is depending on the experience and repeated plugging which lead to serious problems such as longer construction period and lower successful rate of sealing. Therefore, finding a way to improve the success rate of plug mission is a world-class problem. Pingya Luo, a member of the Chinese Academy of Engineering, has put forward the plugging principle of separating-type gel slug. At the same time, Pingya Luo has developed a special plug agent-special gel named ZND. It has been successfully used in the field application. But there is a lack of comprehending of the plugging mechianism of the special gel, there is neither aconclusion to summarize the properties of the special gel ZND which satisfy the requirements of the necessary conditions to plug the vicious lost circulation or appropriate instruments to estimate the properties thus can’t be spread throughout the country. It’s necessary to summarize the properties of the special gel ZND and find appropriate ways and instruments to estimate the properties for the use of the polymer in the plugging vicious lost. It could provide theory support for the filter and standardize of the polymer which can be used used in the plugging vicious lost.This paper has ensured the index of the special gel ZND through research on its molecular structure. The major of them are viscosity, viscoelastic property, gel strength, threshold pressure, supplanting ability and discharge. To be clear about instruments, conditions and scopes of each index. This article tried to establish an initial standard of the properties of the polymer which can used in the plugging vicious lost, instruments and methods to estimate the properties.Study on the vioscity, viscoelastic property and gel strength with ready made instruments. Rheometres like HAAKE RS6000and Grace M3600can be used to investigate the influence of concentration, temperature and shear rate. Thereinto, the former one focus on viscoelasticity while the later one study on the impact of the viscosity caused by concentration, temperature and other facts. Estimate the effects on the gel strength caused by concentration, temperature and other facts by using the Gel Strength Instrument, made by SHEEN.As for threshold pressure of ZND, verify the applicability and repeatability of the instrument, Gel Threshold Presure Instrument, developed for it. Study the influence on the data caused by temperature. In order to measure the threshold pressure in wide crack and fracture-vug reservoir, we restored fractured formation by applying sand blasting that can make simulated crack rougher.To carry out research on the supplanting ability of ZND, the author simulated fractured and fracture-vug reservoir based on apparatus made for them and estimate the supplanting ability by investigate the difference between the simulated formation water volume and gel drainage water volume.The mesh cage with5cm of the length, width and height is made of0.2mm wire diameter20mesh screen. The dilution degree of the special gel is characterized through the difference of quality between before and after the dilution of the gel. Consider the time of the dilution degree over50%as the criterion of the anti-dilution ability. Confirm the conditions of the estimating of the anti-dilution ability.Furthermore, we come out with preliminary criterion of performance index, instruments of evaluation and method of evaluation of ZND according to its scope of performance evaluation results and corresponding evaluation criteria. |
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