Stability Analysis of Near-Wellbore Reservoirs Considering the Damage of Hydrate-Bearing Sediments

Abstract

The stability of hydrate-bearing near-wellbore reservoirs is one of the key issues in gas hydrate exploitation. In most previous investigations, the damage evolution process of the sediment structure and its effect on near-wellbore reservoir stability have been neglected. Therefore, the damage variable is introduced into a multi-field coupled model based on continuous damage theory and multi-field coupling theory. A thermo-hydro-mechanical-chemical (THMC) multi-field coupling mathematical model considering damage of hydrate-bearing sediments is established. The effects of damage of hydrate-bearing sediments on the thermal field, seepage field, and mechanical field are considered. Finally, the distributions of hydrate saturation, pore pressure, damage variable, and effective stress of a near-wellbore reservoir in gas hydrate exploitation by depressurization are calculated, and the stability of a hydrate-bearing near-wellbore reservoir is analyzed using the model. Through calculation and analysis, it is found that structural damage of hydrate-bearing sediments has an adverse effect on the stability of hydrate-bearing near-wellbore reservoirs. The closer to the wellbore, the worse the reservoir stability, and the near-wellbore reservoir stability is the worst in the direction of minimum horizontal ground stress.

Coastal Geohazard and Offshore Geotechnics

“…The stability of hydrate-bearing near-wellbore reservoirs is one of key issues in gas hydrate exploitation. A thermo-hydro-mechanical-chemical (THMC) multi-field coupling mathematical model considering damage of hydrate-bearing sediments is established in [17]. As reported in the paper, with continuous hydrate dissociation, the cementation of the sediment gradually decreases, and the structural damage gradually increases.…”

“…(2) evaluation of stability of marine infrastructures, including pipelines [6][7][8], piled foundation and bridge piers [9][10][11][12], submarine tunnel [13], and other supported foundations [14]; and (3) coastal geohazard, including submarine landslide and slope stability [15,16] and other geohazard issue [17,18]. More details of each contribution are summarized in the following subsections.…”

Statistical damage constitutive model based on self‐consistent Eshelby method for natural gas hydrate sediments

“…Based on experimental measurements, researchers have proposed different types of constitutive models to quantitatively describe the geomechanical behavior of NGH sediments, including nonlinear elastic model, 26 elastic-plastic model, 24,[31][32][33][34] damage statistical constitutive model 35,36 , and critical state model, 25,[37][38][39][40][41] which is an active area in recent years. There are mainly three key issues for the constitutive model of NGH sediments: the effects of saturation and cementation of NGH, the critical state of NGH, and the damage description.…”

“…And some researchers also integrated models of the critical state soil mechanics to describe the inelastic mechanism. [45][46][47] Zhang et al 36 further developed the damage statistical constitutive model of NGH sediments to include the influence of damage threshold and residual strength. Although lots of efforts have made on the constitutive model of NGH sediments, it is still not fully solved and far from satisfactory due to its complexity.…”