A Discussion on the Effects of Hydraulic Fracturing of Laterals on Offset Wells
Well interference is becoming a more evident observed phenomenon in the oil and gas fields. With the growth in unconventional well development and hydraulic fracturing, there is a noticeable rise in well interferences. There are various data representations that display the effect of inter-well communication on pressure, fluid production, and water flooding in the wellbore. Hydraulic fracturing of laterals has an effect on offset wells, but the extent and conditions at which they occur are unknown. This paper intends to provide a deeper understanding on the extent of these observed properties, as well as potential factors that could intensify the interference with the offset wells from the laterals. Some of the affects studied include, how production of the offset wells are deferred due to nearby frac on lateral wells, fluid levels rising in wellbore, water flooding in production fluids, and pressure build-up both downhole and at the surface. Additional affects that may be correlated with fracs may be formation fluid invasion in the wellbore, and corrosion on equipment downhole due to various corroding factors found in these fluids. The intensity of well communication is more predominant with a decrease in well spacing. It is important to determine the minimum distance between laterals in well pads to achieve maximum efficient recovery, which has proved to be a challenge due to the varying components in the subsurface that affect the interference. This study highlights the ‘frac-hit’ outcomes observed on the offset wells from the neighboring wells being hydraulically fracked, and the various impacts observed in production during and after a ‘frac-hit’ on an offset well. An observation of the geomechanical impacts around parent well has shown both enhancement of the permeability in some situations and a decrease in permeability in other situations. Another factor observed was water invasion and its potential to become an oil trapping mechanism. With pressure surges from the fractures, and its distribution through the formation potentially reaching depleted offset zones, it has been found that water can be a factor that is pushed toward the depleted zone. With the water invasion, the fluid levels may rise past perforation zones in the offset, adding potential alternate routes for the water to flow to. If the water flows and enters through the offset fracture networks, it can trap oil and block its entry into the wellbore. An additional observed property included gas trapping mechanisms when well interference occurs below the producing well’s bubble point. Below the bubble point, vapor begins to form, introducing gas into the system. This gas in the formation is now an additional factor that must be observed, and could defer production as well. With a growth in number of wells and well-pad density, the potential for inter-well communication will be greater too. Hydraulic fracs could lead to communication between various wells depending on well spacing, landing, completions, pad sequence, and other factors. An additional factor that needs to be taken into consideration is the correlation between fracture hits and the matrix permeability, as the complexity of fracture networks can vary substantially. We need to understand the effect of various fracture networks as well as increasing matrix permeability. It is observed that an intensification of fracture connectivity, can cause a pressure drop in adjacent wells. It is important to understand frac geometry from different perspectives, hydraulic, propped, and conductive fracs, which would help give a better understanding of how to better construct the completion design. Multiple variables need to be evaluated in an attempt to optimize the well completion. In summary, this paper tries to provide a deeper understanding on a variety of interferences and effects of hydraulic fracturing of laterals on offset wells.
AAPG Datapages/Search and Discovery Article #90370 ©2020 AAPG Middle East Region Geoscience Technology Workshop, 3rd Edition Carbonate Reservoirs of the Middle East, Abu Dhabi, UAE, January 28-29, 2020