Numerical analysis on gas production performance by using a multilateral well system at the first offshore hydrate production test site in the Shenhu area

First Offshore Gas Hydrate Production Test in the South China Sea: Numerical Simulation of Production Behavior with Different Multicluster Well Patterns

“…However, for the multicluster well production mode, the mechanism of increasing production is mainly based on the expansion of drainage area, and the production efficiency improvement of different well-net patterns is not proportional to completion length. Therefore, the production index J is proposed as an auxiliary indicator to evaluate the yield increase effect of NGH in this work. , The particular production index is defined as follows: J = Q g / h normalΔ P where h is the effective completion length (m), and Δ P is the pressure difference (MPa). The index J is mainly related to the well type and drainage area, which can reflect the yield-increasing effect of different well types. , Different well-net pattens were produced within 1080 days, as indicated in Figure .…”

“…Therefore, the production index J is proposed as an auxiliary indicator to evaluate the yield increase effect of NGH in this work. , The particular production index is defined as follows: J = Q g / h normalΔ P where h is the effective completion length (m), and Δ P is the pressure difference (MPa). The index J is mainly related to the well type and drainage area, which can reflect the yield-increasing effect of different well types. , Different well-net pattens were produced within 1080 days, as indicated in Figure . Well spacing is a major factor affecting productivity under the preconditions of fixed well-net pattern and pressure difference, and the wider the well spacing, the higher the productivity and the larger the J -index.…”

“…The three layers of the NGH reservoir model are depicted in Figure a and have thicknesses of 35 m for GHBL, 15 m for TPL, and 27 m for FGL. ,− Based on the logging curve (Figure a), extracting the saturation data of these three layers at intervals of 0.5 m for the numerical models, the mean permeabilities of GHBL, TPL, and FGL were 2.9, 1.5, and 7.4 mD, respectively. ,− Since the permeability of the OB and UB layers in this study was lower than that of GHBL, TPL, and FGL, its value was logically set to 2.0 mD. The porosity of the overburden and underlying layers in this study is set the same to 0.3. ,− Table provides a summary of the key simulation parameters and the reservoir model’s physical attributes.…”

“…Therefore, the production index J is proposed as an auxiliary indicator to evaluate the yield increase effect of NGH in this work. 10,31 The particular production index is defined as follows:…”

“…The index J is mainly related to the well type and drainage area, which can reflect the yieldincreasing effect of different well types. 10,31 Different well-net pattens were produced within 1080 days, as indicated in Figure 10. Well spacing is a major factor affecting productivity under the preconditions of fixed well-net pattern and pressure difference, and the wider the well spacing, the higher the productivity and the larger the J-index.…”