Well Integrity for Fracturing and Re-Fracturing: What Is Needed and Why?

Abstract

Abstract Fracturing, multiple fracturing and refracturing often create peak loads for well design. The scope of this work is to identify areas of potential damage in older wells being considered for refracturing so that those wells can be flagged for further investigation and repair. Removing damaged well stock from consideration before a well integrity failure can occur protects the environment and also allows time for repairs that protect the future value of the well stock. New and older well conditions and stimulation methods are discussed with a view towards identifying peak-load factors. Laboratory work and literature study results are also cited to document the connection to previous work and relate literature findings to current stress load causes and isolation damage prevention. Well integrity investigation methods include pressure testing, cement evaluation tools (CET), cement and stimulation pump charts, downhole imaging devices (cameras, calipers, electrical logging tools), and other approaches. New well fracturing, and particularly multi-fracturing completions can produce stresses on the cement-to-pipe and cement-to-formation seals, although the damage, depending on specific conditions can be minor to moderate and changes to construction techniques can eliminate or minimize most problems. Re-fracturing of wells opens several new areas of concern including corrosion, erosion, and production related issues such as subsidence that may result in a higher risk to barrier elements. The results of the work illustrate construction methods that can produce wellbores capable of handling significant multi-fracturing stimulation. In addition, risks of re-fracturing damage on damage to older wells are rated with monitoring and remedial operations as part of the discussions. Finally, frac hits (a fracture from one well intersecting and damaging an adjacent well) will be discussed with examples of several factors that are common in frac hits.