In recent years several papers have been written on the merits of fracture stimulation with crosslinked methanol. While crosslinked methanol has been available to the industry since the late 1980's, only in recent years has it been successfully and routinely utilized in the continental United States. In areas such as the Permian Basin it was thought that the best application for crosslinked methanol would be in older wells, or in new wells drilled in under-pressured Morrow reservoirs. It was not until the case history wells in this study had been treated that the fluid was proven to be successful on new and relatively undamaged Morrow reservoirs.
This paper will discuss the fluid system with focus on recent refinements in fluid chemistry. Special attention will be given to standard procedures implemented to ensure the system is pumped safely. An overview of the reservoirs where crosslinked methanol has been applied successfully, along with treatment parameters will be discussed. Finally, a production study of the case history wells relative to offset Morrow producers will be reviewed.
Crosslinked methanol has been available as a stimulation fluid since the late 1980's. However, widespread usage in the continental United States has not been the case. The lack of extensive usage is due to a multitude of reasons and related perceptions. Crosslinked methanol will never take the place of standard water-based fracture fluid systems due to their wide application range and relative low cost. Standard foam fluids have a long history of success and provide certain advantages that can only be realized by energized fluid systems. Oil-based fluids, emulsions, water-based crosslink fluids, linear fluids, and more recently non-gelled water fluids have all found areas of application where they may claim supremacy. Crosslinked methanol is no different in that it too has found niche applications where it is proving to be the fluid of choice, and where relative results are undeniable. One of these applications at present is the Morrow formation of Southeast New Mexico. It is not suggested that all Morrow wells be stimulated only with crosslinked methanol. Quite the contrary, it is in some Morrow formations that exhibit certain reservoir characteristics that crosslinked methanol has found success. Like any fluid system, crosslinked methanol is no "silver bullet." All fluid systems should be applied with reservoir parameters and treatment goals in mind. Crosslinked methanol simply provides another choice, and another tool, when addressing a reservoir for a potential fracture stimulation treatment. Reservoir parameters should always be the driving force behind fracture stimulation design and subsequent fluid selection.
Methanol as a stimulation fluid has long been a respected application in the oil industry. Historically, methanol has been used in remedial applications, and in most cases it has been used to take advantage of its low surface tension properties. The surface tension properties of pure methanol have been measured in the laboratory at 22.6 dynes/cm, relative to fresh water at 72.7 dynes/cm. Another application of methanol is to prevent the introduction of water to supposed water sensitive formations during stimulation or workover operations.