The results of 277 wells cemented in Daniudi gas field indicate that 92. 7% have high quality and 100% meet the specified requirement, and the most important is that the pollution depth by cement slurry is only 5. 16 cm which can be removed completely by perforation.

Based on experiments, according to the relationship between the permeability damage rate and the every factor of the reservoir, the inherent relation between the indexes of reservoir pollution evaluation is studied deeply, and the quantitative calculating model is developed between the evaluation indexes of permeability damage rate, pollution skin factor, pollution depth of drilling fluid, and the parameters of logging, drilling, reservoir physical property and electrical property.

This paper analyzed the characteristics of horizontal wells d amage, an d then established a set of method to calculate the drilling fluid lost circulat ion and pollution depth that vary with the horizontal section.

Applying the theoretical model to calculate the equifinal damage depth which varies with the horizontal section, a formula of pollution depth which varies w ith the horizontal section through volume transformation was presented.

On the basis of the hole-buttom model experiment, this paper studies the damage of mud and cement slurry to foemation. The study shows that the damage of mud is more serious than that of cement slurry. Since the aggressive quantity of cement particles and filtrate is limited by the percolation properties of inner and outer mud cakes and rock core, the damage of cement slurry to formation is therefore decresed. The damage in the area 122 cm inside the wellface is resulted mainly from plugging of grain, while...

On the basis of the hole-buttom model experiment, this paper studies the damage of mud and cement slurry to foemation. The study shows that the damage of mud is more serious than that of cement slurry. Since the aggressive quantity of cement particles and filtrate is limited by the percolation properties of inner and outer mud cakes and rock core, the damage of cement slurry to formation is therefore decresed. The damage in the area 122 cm inside the wellface is resulted mainly from plugging of grain, while the damage to the formation 2 cm away from the wellface is resulted from the precipitates of filtrate of cement slurry. This paper also analyzes the pollution depth, the filtrate composition, the quantity of precipitates, and the separation sequence.

This paper analyzed the characteristics of horizontal wells d amage, an d then established a set of method to calculate the drilling fluid lost circulat ion and pollution depth that vary with the horizontal section. Based on the lost circulation characteristics of drilling fluid and law of conservation of mass, by way of Cart model that applies in the fracture fluid lost, the paper came to a mathematics model of drilling fluid lose that varies with the horizontal secti on. Applying the theoretical model...

This paper analyzed the characteristics of horizontal wells d amage, an d then established a set of method to calculate the drilling fluid lost circulat ion and pollution depth that vary with the horizontal section. Based on the lost circulation characteristics of drilling fluid and law of conservation of mass, by way of Cart model that applies in the fracture fluid lost, the paper came to a mathematics model of drilling fluid lose that varies with the horizontal secti on. Applying the theoretical model to calculate the equifinal damage depth which varies with the horizontal section, a formula of pollution depth which varies w ith the horizontal section through volume transformation was presented.

It is important work for reservoir protection to evaluate reservoir pollution level by drilling fluid. It is an economic and effective tool to evaluate the reservoir pollution level directly or indirectly with logging data. Based on experiments, according to the relationship between the permeability damage rate and the every factor of the reservoir, the inherent relation between the indexes of reservoir pollution evaluation is studied deeply, and the quantitative calculating model is developed between the evaluation...

It is important work for reservoir protection to evaluate reservoir pollution level by drilling fluid. It is an economic and effective tool to evaluate the reservoir pollution level directly or indirectly with logging data. Based on experiments, according to the relationship between the permeability damage rate and the every factor of the reservoir, the inherent relation between the indexes of reservoir pollution evaluation is studied deeply, and the quantitative calculating model is developed between the evaluation indexes of permeability damage rate, pollution skin factor, pollution depth of drilling fluid, and the parameters of logging, drilling, reservoir physical property and electrical property. With programming calculation and real data analysis, it is found the evaluation method is correct and feasible. And the judge standards of reservoir pollution level by drilling fluid can be derived by the method for a concrete drilling region, which can provide the important basis for scientific decision making of drilling, perforating and stimulating operations in the region.