Abstract
During field development planning, the condensate blockage phenomena often receives minor attention leading to overestimation of the gas well deliverability. This study addresses the numerical analysis of both the risk potential of condensate blockage and the complex physiochemical processes of nanofluid treatment for two very different gas condensate fields.
Producing gas condensate reservoirs below the dew point results in condensate dropout and liquid holdup, which usually impairs the gas flow significantly. Wintershall Dea is currently investigating the feasibility of a nanofluid huff’n’puff treatment which aims to alter the wettability in the near-wellbore area, so that both water and condensate are repelled by the rock surface. For accurate representation of condensate blockage, Generalized Pseudo Pressure (GPP) along with local grid refinements (LGRs) were incorporated in the compositional model as well as high-velocity effects and a detailed post hydraulic fracture environment. The limitations of commercial simulation software in representing the nanofluid treatment in the dynamic reservoir model were overcome by combining the implementation of new hydrocarbon components, the surfactant model, tracers, chemical reactions, and special-purpose Python scripts.
The buildup and spatial distribution of the condensate in and around the well and the fracture was analyzed. The two key parameters influencing the severeness of condensate blockage comprise the composition of the reservoir fluid and the effective permeability of the gas phase, which are particularly influenced by multiphase flow behavior, formation and/or fracture damage, high-velocity flow effects, and subsurface equipment like gravel packs. In both reservoirs studied, wells were identified that will most likely experience significant productivity impairments due to condensate blockage, some already a few months after the start of production and some in the next few years.
The transport of the active nanofluid chemical was implemented by two different approaches: for one it was carried by a solvent system, and for the other it was dispersed as droplets in gas. Both approaches mainly differ in the depth of penetration and the propagation of the nanofluid as well as in the operational effort and the longevity of the wettability alteration. The nanofluid treatment cases demonstrated promising preliminary results with an increase in gas productivity index up to 30%.
The removal of condensate blockage using a novel wettability altering nanofluid formulation was initially conceptualized and subsequently analyzed for vertical wells and hydraulic fractures using numerical simulation. For the first time, a comparison between the injection of the active nanofluid within either a gas or solvent carrier was evaluated. The risk of condensate blockage and a potential treatment were analyzed for real case scenarios including promising business viability.
