Abstract: Reasonable well pattern density is pivotal decision-making parameter at oilfield development first stage. Whether it is exact directly connect with the number of wells, especially in small fault-block oilfield, in the case of small number of wells, one or two wells directly affect economic benefit. Applying to Srkachef relational expression, we regress experiential expression of mobility and index of well pattern which meets combining economy estimating, the expression of well pattern density is built in oilfield development first stage. The reasonable well pattern density may be determined by graphic approach, and it can provide foundation for whole pattern deployment at oilfield development first stage.