Research And Application Of Equilibrium Pressure Cementing Techniques Of Gas Field In Northern Ordos

In this paper, the author focused on the comprehensive study of Gas Field in Northern Ordos which is low gas pressure, low permeability, dense gas field, etc. And considering about several factors, such as formation characteristics, water quality, factors of gas cut and gas channeling. And combining with the slurry system used in history, cementing techniques, and characteristics of leakage of fractional gas wells. To developed the middle layers of water cement slurry system and sealing segment cementing slurry system, even developed the supplementary cementing technique which is fit for the Gas Field in Northern Ordos. Key features of low density slurry system:density:1.23-1.28g/cm, dehydration:≤50ml/70℃/6.9Mpa, initial consistency:<20Bc, free water:<0.2ml, compressive strength:≥3.5MPa/70℃/24h/Pressure; Key features of Cementing gas segment slurry system: density:1.87-1.90g/cm, dehydration:≤30ml/70℃/6.9Mpa, initial consistency:<20Bc, free water:=0, compressive strength:>22.5MPa/70℃/24h/Pressure。Through the summary analysis of the laboratory study and site construction, the paper showed us that we have mastered the pressure field cementing process control technology of Gas Field in Northern Ordos. It includes the pressure prediction during the process of cementing replacement and calculation of pressure stability of the section of gas slurry system. And we designed the length and density of each section of cementing formed the gas slurry system and designed the construction site of Gas Field in Northern Ordos.According to the study, there is no leakage occurred of any well during the cementing process in2008-2009. This also proves the rationality of the design field cementing. At the same time, the quality cementing of the Gas field in Northern Ordos have been greatly improved. Up to now, we finished180wells, only two wells are just qualified,5good wells, and the remaining wells are high-quality. The rate of high quality is higher than96%,the rate of good quality is greater than98%, the rate of pass cementing is100%. Once a time, during the process of cementing, we found the maximum leakage pressure during the cementing of Gas Field in Northern Ordos. This sucess set a good example for the later cementing.