Special core analysis designed to minimize formation damage associated with vertical/horizontal drilling applications

Laboratory testing of core material to optimize drilling fluid composition and procedures has been used for many years to minimize invasive formation damage of a mechanical, chemical or biological nature which can occur durin g the drilling of horizontal or vertical wells. This paper discusses the li mitations of past practices such as the use of non-representative core or f luids, non-preserved or non-restored state core, ambient conditions of temp erature and overburden pressure, direct injection of muds/filtrates into sa mples and unrealistically high drawdown gradients for cleanup. The paper de scribes the current technology used to eliminate many of these concerns and also to extend drilling fluid evaluation technology to extremely heterogen eous carbonate and sandstone formations, fractured formations and specific test equipment and procedures used to evaluate the effectiveness and utilit y of underbalanced drilling programs.