Early completions in the Marcellus formation consisted of long stage sections (up to 450 ft between injection points) with few entry points in an effort to complete the wells in a timely fashion. Volumes of fluid and proppant were a function of the number of stages based on the geometric division of the wellbore. Concerns regarding stress shadowing and proppant placement outweighed formation considerations at that time. In many cases, economics were a driving factor with respect to the number of stages an operator was willing to perform. With increased equipment availability, job costs decreased and operators performed more stages per well with shorter spacing between clusters. Initial production figures confirmed the need to shorten cluster spacing and stage lengths; but, questions remained regarding the previous wells treated with longer stages and larger spacing between clusters and whether these wells still had commercial quantities of gas to be accessed.
Since November of 2013, seven wells were restimulated using a new diversion process that allowed the operator to reduce the cluster spacing. In one case, the original failure to reach total depth (TD) with casing provided an opportunity to stimulate new areas of the rock in an openhole environment. This paper details the process applied to the seven wells and confirms access to significant additional reserves based on production results. Use of an analytical production simulator confirms improvement to the productivity index (PI) and EUR30 forecast. One operator has confirmed more than 200 candidates for this refracturing process.