Slimhole Cementing - Analysis and Possible Solution of the Problem

Abstract

Abstract Very little quantitative data are available on how to cement slimhole wells while still adhering to good cementing practices. Therefore, a combined theoretical and experimental study has been carried out, from which a number of slimhole cementing guidelines have been derived. The analysed example case considered the cementation of a 3−1/2" liner in a 4−1/8" hole, in a relatively deep, high pressure, high temperature well drilled in a formation with minimal difference between pore and fracture pressure gradients. It was found that a conventional (solids laden) high pressure, high temperature (HPHT) water-based drilling fluid cannot be fully displaced by the cement slurry, without exceeding the pressure limits of the formation. On the other hand, a potassium formate brine based HPHT drilling fluid can be displaced with close to 100% efficiency, even with sub-optimum cementation practices (i.e. no pipe movement, low annular velocity of the mud in the initial stage of the cementation). The low, flat gels and thin, tough filtercake greatly facilitate mud removal during cementing.