Maintaining Horizontal Well Stability During Shale Gas Development

摘要

Along with the development of unconventional resource, an increasing number of researches and field operations have been focusing on horizontal shale gas well. The most crucial element of a horizontal well is to enlarge the drainage area, subsequently enhance the well productivity. The technique of hydraulic fracturing has been accepted as an industry standard in developing shale gas play. Therefore, the casing-cement-shale system in the horizontal well should be able to survive from any potential variation of temperature and pressure during well stimulations. The current horizontal well design for casing burst resistance and collapse resistance have been improved by some researchers. Little research can be found to consider the mechanical behavior of shale during the development of a horizontal shale gas well. This paper focuses on the instability of shale behind the casing and cement in a horizontal shale gas well. The variation of Von-Mise stress with time resulting from the wellbore flowing fluid in the horizontal well is predicted. The proposed model also quantitatively elaborates the difference of temperature distribution in horizontal shale cased hole and open hole. Well stimulation fluid with lower temperature is found to increase the risk of failure in the horizontal shale well. With the model, the down-hole instability of shale gas play in horizontal wells can be evaluated confidently.