It is usually desirable to defer water coning onset or rise as long as possible while water production is an inevitable consequence when producing oil from a bottom-water drive reservoir. Numerous mechanical and chemical methods have been employed to achieve this goal over the years. This paper presents a new insight into field implementation to improve oil production and ultimate recovery by reducing excessive water production utilizing the low permeability flow barriers, especially the natural ones such as shale bodies, below the horizontal well trajectory.
In this study, a 3D numerical simulation model using Computer Modelling Group's (CMG) STARS Simulator was generated as a cost effective way to investigate the effects of the different horizontal shale bodies on horizontal well performance in a bottom-water reservoir; field experience and researches from other investigators have shown the extremely low permeability of shale body. This fact and other relevant factors are comprehensively considered when horizontal well technology is applied to develop the bottom-water reservoirs. For all of the simulation cases studied, the results have indicated that water cut can be postponed and reduced largely, the cumulative oil production is increased and the cumulative water production is decreased dramatically, when there are barriers existed underneath the horizontal producer. This encouraging idea has been further studied numerically to seek the possibility of field implementation in conventional and heavy oil reservoirs, including the application of fractured horizontal well, small-scale CO2, steam and solvent injection.
This new strategy could be a very promising and economic way to develop reservoirs with active bottom water, especially for those with strong bottom-water support. It deserves a thorough research from reservoir characterizing, field implementing, lab investigating, simulation studying and other various aspects. This article has analyzed numerically the effects of shale bodies and other related technologies that may be implemented in the field. The results and understandings acquired from the study will orientate our next steps. Our future work will focus on the identification and involvement of the natural flow barriers (NFB) by integrating information from well testing analysis and well logging interpretation, and on the experimental studies of field implementation strategies using the artificial flow barriers (AFB) in different well pattern systems.
Water coning is a critical issue for conventional vertical wells producing under bottom-water reservoir condition. The phenomenon of water coning can cause increased water production and shorten the life of the well. The application of the horizontal well technology is attractive because of its expected higher productivity and the benefits of reducing water coning. However, water crest and breakthrough into the 2 horizontal well is still a major concern in bottom-water reservoirs, especially for those reservoirs with strong bottomwater support.
It is commonly recognized that the water coning could be controlled or suppressed by means of horizontal barriers, either natural barriers or artificial barriers. In other words, the natural barriers such as shale streaks and formation bodies with low permeabilities are helpful in restricting bottom-water production. Their presence will increase the tortuosity of fluid flow paths, and thus decrease the effective single-phase permeability of the reservoir (1–8).
