Well planning The drilling of a well involves a major investment, ranging from a few million US$ for an onshore well to 100 million US$ plus for a Deepwater exploration well. Well engineering is aimed at maximizing the value of this investment by employing the most appropriate technology and business processes, to drill a ‘fit for purpose’ well, at the minimum cost, without compromising safety or environmental standards. Successful drilling engineering requires the integration of many disciplines and skills. Successful drilling projects will require extensive planning. Usually, wells are drilled with one, or a combination, of the following objectives: to gather information to produce hydrocarbons to inject gas or water to maintain reservoir pressure or sweep out oil to dispose of water, drill cuttings or CO2 (sequestration). To optimize the design of a well it is desirable to have as accurate a picture as possible of the subsurface. Therefore, a number of disciplines
Although the drilling of a well is a complex operation involving many different mechanical elements and processes, the single most important factor upon which the successful completion of the well depends is the drilling-fluid circulation system. The majority of serious problems encountered during drilling, including lost circulation, stuck pipe, kicking wells, poor penetration performance, high costs, blowouts, and poor-quality well logs, can all be traced back to poorly designed, misunderstood, and misused drilling-fluid systems. The primary functions of the drilling fluid and its circulation systems are: 1. To remove rock cuttings from the bottom of the hole so that the bit can drill on a fresh rock surface, thereby increasing the efficiency of the drilling operation. 2. To transport the cuttings to the surface where they can be removed from the drilling fluid. 3. To suspend the cuttings in the hole whenever mud circulation is stopped. 4. To cool and lu