Controlling Proppant Wettability Leads to Increase Flowback Recovery and Flow in Frac-Packs

Abstract

Recovery of frac-pack fluids is often poor in offshore operations. Large amounts of stimulation fluids left in the fracture may leak-off into the porous formation or block part of the proppant pack thus impairing hydrocarbon production. A typical frac-pack treatment fluid contains water-wetting surfactants to maximize flow-back fluids. However, the amounts recovered are still low and new methods are needed to improve well cleanup. Using a proppant that is neither oil nor water wet has the potential to solve some of these issues. Proppant surfaces were permanently modified to a neutral wettability state. Molecules having both hydrophobic and oleophobic properties were covalently bonded to the oxide surfaces, leading to robust engineered interfaces with low surface energy thus potentially improving flow. To support this concept of neutral wettability proppant, laboratory studies were conducted to determine performance under flow and cleanup ability compared to native proppant surfaces. This neutral wettability proppant was also used in several completions in the Gulf of Mexico. Two case histories using the neutral wettability proppant are presented and compared with offset wells as well as performance laboratory data. Flowback data as well as production data are reported. Laboratory results showed that the neutral wettability enhanced surfaces not only reduce water saturation but also improve oil movement. This demonstrates the ability of these materials to improve clean up and hydrocarbon flow within the proppant pack. When this proppant was applied in frac-pack completions it was observed that flow-back recovery was dramatically increased compared to offset wells that used similar proppant. Cleanup time was reduced allowing first oil to appear more rapidly. Furthermore, production data show that oil flow that the productivity index is higher when the surface of the proppant is neutral. These results demonstrate this material as next generation proppant for improving flow and cleanup in frac-pack completions.

Effect of surface wettability of ceramic proppant on oil flow performance in hydraulic fractures

“…[26][27][28][29] In the hydraulic fracturing process, the water entrapment can lead to a high pressure loss of the fracturing fluid within the proppant pack and a decreased fracture length. However, due to the highly water-wet surface of natural proppants, the traditional proppants can easily retain the water phase within the proppant pack.…”

“…[26][27][28][29] In the hydraulic fracturing process, the water entrapment can lead to a high pressure loss of the fracturing fluid within the proppant pack and a decreased fracture length. [26][27][28][29] Designed for eliminating the capillary pressure, the neutrally wet surface has no preferential affinity for both the aqueous phase and hydrogen, simultaneously being hydrophobic and lipophobic. 26 To reduce the amount of the water entrapment within the proppants pack, the neutrally wet proppants are encouraged by many scholars and the industries.…”

“…[8][9][10][11][12][13][14][16][17][18][19][20][21][22][23][24][25] Moreover, the intermediate strength ceramic proppants should be more durable than clay-based ceramic proppants and sand proppants under cyclic stresses. 26 To increase the flow back recovery, Bestaoui-Spurr et al [27][28][29] developed a neutrally wet proppant by bonding the hydrophobic and oleophobic molecules to the proppant surface and demonstrated it could significantly fasten the fluid movement and the clean-up of treatment fluids by eliminating the capillary pressure. The available studies of proppant wettability are mainly relevant to the clean-up of fracturing fluid residues inside the fracture.…”

Effect of surface wetting behavior of ceramic proppant on the two‐phase flow across the interface of sandstone and fracture

“…For the flow across the fracture surface, oil‐wet surface attracts oil and repels water from the sandstone, forming an oil channel across the fracture surface. The true effect of flow across the fracture face can be masked in the investigations by Bestaoui‐Spurr et al and Bestaoui‐Spurr where both sandstone reservoirs and hydraulic fractures are in much larger scale than the fracture faces.…”

“…This tends to be consistent with Wang's work. The investigations by Bestaoui‐Spurr et al and Bestaoui‐Spurr for the effect of proppant wettability on the water recovery during flowback and the flow in frac‐packs in real wells show that neutral wettability surfaces reduce water saturation in the fracture and improve oil flow. Their findings seem to confirm the work of Mora et al Apparently, the results from previous investigations about the effect of surface wetting property on oil flow are conflicting.…”