Underbalanced drilling becomes very famous in several places of the world because there are some advantages over normal drilling operations. Today we would like to share the basic underbalanced drilling 101 for everybody who is interested in this topic. It is presented by Shell and we also add full VDO transcript for anybody who cannot catch the information from this presentation.
Underbalanced Drilling 101 Full VDO Transcript
This presentation introduces the concept and equipment used in underbalanced drilling operations. The key differences between underbalanced drilling and conventional overbalanced drilling are at both the conceptual and the technical level. At the conceptual level the subsurface drilling conditions needs to be investigated further, the rotating drill bit cuts away rock to deepen the well. The drill cuttings are lifted to the surface by the circulating drilling fluid.
Underbalanced drilling is a drilling technique that hydrostatic pressure from drilling mud is less than reservoir pressure. The underbalanced drilling can be created by using low weight fluids as base oil, fresh water which has less hydrostatic pressure than the expected formation pressure. Additionally, this drilling method is achieved by using low density drilling fluids as gas, foam, combination between conversional drilling fluid and foam/air.
The main advantage of Underbalanced drilling is to minimized formation damage in reservoir. With underbalanced drilling, the reservoir fluid is allowed to flow out into the well therefore the chance of mud invasion into the reservoir is minimal. Hence, the production from the well from this technique is higher than normal wells. Conversely, drilling with conventional method (overbalanced drilling) creates near wellbore damages which affect hydrocarbon production.
The underbalanced drilling is often applied to horizontal drilling wells because long horizontal reservoir will not be damaged with drilling fluid. Only few inches of near wellbore damage in the horizontal section can drastically reduce the reservoir performance.
This video from Shell demonstrates you regarding underbalanced drilling and there is one section showing comparison between conventional and underbalanced drilling. This short VDO will definitely give you clear picture of this technique.