Straddling the south coast of England, the Wytch Farm oilfield has been producing from the heterogeneous Sherwood Sandstone reservoir since 1990. This complex reservoir features a mix of multistorey, multilaterally braided channel, sheetflood sandstones and widespread ephemeral lacustrine mudstones, resulting in a layered flow regime with poor vertical permeability (Fig. 1).

With 58% of reserves and the best channel sands located offshore, an artificial island was proposed in 1993 to access these lucrative reserves from 40 wells. However, advancements in technology led to a more economical solution: extended reach drilling (ERD).

These wells were drilled onshore to record breaking lengths, with the final well extending 10.7 km in length (11.3 km MD) at an 86° angle from vertical. For wells longer than 8 km, inverted tails were utilized to penetrate the less desirable upper layers (Fig. 2).

As a result of ERD, by 2003, 73 more wells had been drilled to target the offshore reserves, significantly increasing production from 67,336 BOPD to a plateau of 97,649 BOPD between 1995 and 1998 (Fig. 3).