Design And Software Development Of Culvert Cement

Squeeze-cementing is one way of well cementation.It is widely applied in the field, including the entire operation links of drilling,well cementation,well completion and workover. Squeeze-cementing is a complicated operation that is usually applied in unfavorable wellbore conditions.The success rate of squeeze-cementing is relatively low and the failure occurs frequently, which will not only increase the cost, but also restrict the better application in the field. After years of research conducted by many scholars and field engineers both domestic and foreign, a certain system of squeeze-cementing techniques has formed. However, the past research mainly focused on material system and squeeze-cementing technology, hardly touched upon the theoretical calculation of squeeze-cementing. Although the squeeze-cementing plays a vitally important role now,it is always in a very embarrassing situation and doesn’t arouse enough attention.Therefore, the study on the squeeze-cementing calculation is important to improve the success rate of squeeze-cementing.Theoretical calculation of squeeze-cementing is based on the squeeze-cementing techniques in the field.This thesis sums up the squeeze-cementing technology mainly from the four perspectives of the squeeze pressure, squeeze tool, pumping technique, displacing technique.analyses the characteristics and application conditions of various squeeze-cementing technology, which provides the theoretical basis for reasonable selection of squeeze-cementing technique and design calculation.Through the squeeze-cementing characteristics, field operation and the past experience algorithms, this thesis establishes a engineering design calculation method of squeeze-cementing, and confirms that different squeeze-cementing have different calculation methods in terms of cement slurry volume, displacement volume and squeeze-cementing pressure parameters.Combined with the practice of squeeze-cementing, the formation initiation pressure prediction model of the casing-cement sheath-stratum with squeezing pressure, in-situ stress and perforation is established in terms of elastic plane strain theory. Meanwhile, the influence of perforation angle, cement slurry filtration, in-situ stress, elastic modulus and Poisson’s ratio of formation and cement sheath on initiation pressure is analysed. Results show that the formation initiation pressure increases with the increase of perforation angle, elastic modulus and Poisson’s ratio of formation, and decreases with the increase of in-situ stress heterogeneity, elastic modulus and Poisson’s ratio of cement sheath. And the formation initiation pressure decreases when considering the cement slurry filtration.The calculation relationship of safe squeeze pressure and the initiation pressure prediction model of cement sheath are established, and the influence of in-situ stress heterogeneity,elastic modulus and Poisson’s ratio of formation and cement sheath on initiation pressure of cement sheath is analysed. Combined with the specific examples, the safe squeeze pressure is discussed. Results show that safe squeeze pressure should consider formation initiation pressure and cement sheath initiation pressure, and shouldn’t ignore the cement sheath damage.According to the theoretical calculation models of squeeze-cementing that are established in this thesis, a software is developed, which can improve the efficiency of design calculation.