Formation damage: Do we always need to have a high focus on its prevention, or do occasions exist when it really does not matter? We use significant resources in terms of personnel and testing for the avoidance of formation damage. For new field developments, large studies are undertaken to identify the optimal fluid selection and pumping sequences for producers and injectors. Such studies also ensure compatibility between the fluid candidates and the relevant production/injection intervals and lower completion designs. A similar approach is made when an asset changes fluid vendor.
However, in all this fluid evaluation, do we ever consider the actual significance of formation damage during the well lifetime? Take the example of fluid qualification for a produced-water-reinjection well. We perform corefloods to identify the least-damaging drilling and completions fluids. At the start of injection, we have a well with good injectivity, but, after a few weeks in operation, we notice a sharp decline in volumes being injected. The cause has nothing to do with the drilling and completion fluids but rather the injection of produced water, which, although within specification, contains fines and oil-in-water emulsion that causes formation plugging. This is a common occurrence for many injectors, with fracturing used to increase injectivity. Given that plugging of the injector is expected a short time after the initiation of injection and that fracturing will be used to bypass the damaged zone, is it useful to spend resources on qualifying nondamaging drilling and completion fluids for such wells?
However, many instances occur where inadequate drilling- and completion-fluid evaluation has resulted in significant formation damage with a corresponding negative effect on productivity. Often, finding the specific cause of the lower-than-expected well productivity can prove to be very demanding. Several detrimental factors can act concurrently, or a single cause may be responsible. Typically, these include sand-screen plugging, inadequate cleanup, fluid incompatibility leading to emulsion formation, mud-solids invasion, and excessive fluid losses, among many others. Simulating the downhole operational sequences through coreflood has been used with varying success to identify the cause of the damaging mechanism if it is related to the drilling and completion fluids used.
This Month's Technical Papers
Study Investigates Formation Damage Induced by Water Reinjection in Unconsolidated Sands
Flow-Simulation Model Improves Analysis of Perforated-Rock Cleanup and Productivity
Study of Carbonate Reservoirs Examines Fines Migration in CO2-Saturated-Brine Flow
Recommended Additional Reading
SPE 189483 Perforation Crushed Zone Characteristics in a Subsurface Sandstone by G.G. Craddock, Halliburton, et al.
SPE 185889 The Nature of Drilling-Fluid Invasion, Cleanup, and Retention During Reservoir-Formation Drilling and Completion by Justin Green, Corex, et al.
SPE 189520 Restoring the Auca Field Potential Through Formation-Damage Removal by B. Fun-Sang, Schlumberger, et al.
| Niall Fleming, SPE, is a specialist in production technology with Equinor in Bergen, Norway. He has worked previously as a production geologist, chemist, and engineer. During the past few years, Fleming has worked as a leading adviser for well productivity and stimulation and as lead production engineer for the North Komsomolskoye project in Siberia. His main interest is within the area of formation damage from drilling and completion fluids and in wells under production. Fleming holds a PhD degree in geology from Imperial College London. He has authored several SPE papers, is an associate editor for SPE Production & Operations, serves on the JPT Editorial Committee, and has been a member of the organizing committees for several SPE conferences and workshops. In 2015, Fleming was awarded the SPE A Peer Apart award, and he is a four-time recipient of SPE’s outstanding technical editor award. He can be reached at nfle@equinor.com. |
