Production Analysis Case Study

Sensitivity analysis

The probabilistic analysis provides a better understanding of the likely completion and reservoir parameters. The mean value of the final distribution in Table 1 was fed to the created trilinear composite model to develop a base case scenario. Following that, the sensitivities of the main reservoir and the completion parameters were input into the model, and model was run for the equivalent of 30 years in order to determine the impact of each parameter. Results were plotted on both Cartesian and logarithmic scales and normalized to the base case maximum value to evaluate the performance from different angles. The following results were obtained from the sensitivity analysis.

The production is directly proportional to the fracture half-length. The longer the fracture half-length of the fractures formed, the higher the rate of production and the cumulative production. The ratio of the increase in the production to the increase in the fracture half-length is 1:2 (Fig. 8). The duration of the flow regimes is not affected by the fracture half-length.

Fig. 8

Fracture half-length sensitivity

The production is directly proportional to the number of fractures. More the fractures formed, the higher the initial rate of production and the cumulative production. The increase in the initial rate only lasts for at most a year. The ratio between the production increases after the equivalent of 30 years, and the fracture number increase is 3:5 (Fig. 9). More the number of fractures, the shorter the transition period between the first linear flow and BDF.

Fig. 9

Fracture number sensitivity

The production is directly proportional to the well length. However, the relationship weakens when the well length is longer. The effect of longer wells appears after 1 year of production. The ratio between the increase in the production after 30 years and the longer well is 3:5 (Fig. 10). Longer wells delay the BDF regime and extend the linear flow regime.

Fig. 10

Well length sensitivity

The production is directly proportional to the fracture conductivity. However, the effect of more conductive fractures is negligible and is only apparent for the first few days lasting only for a few months (Fig. 11). Fracture conductivity does not affect the duration of the flow regimes.

Fig. 11

Fracture conductivity sensitivity

The production is directly proportional to the well spacing. The effect of a larger spacing is initially negligible and is only apparent in the last few years of production. However, a small spacing that is really close to the fracture length shortens the well life significantly and thus decreases the production (Fig. 12). Well spacing does not affect the duration of the flow regimes.

Fig. 12

Well spacing sensitivity

The production is directly proportional to the fracture height. The higher the fractures formed, the higher the rate of production and the cumulative production. The ratio of the increase in the production and the increase in the fracture half-length is 1:1 (Fig. 13). The duration of the flow regimes is not affected by the fracture half-length.

Fig. 13

Fracture height sensitivity

The production is directly proportional to the inner permeability. The increase of production due higher permeability is negligible (Fig. 14). The effect of the higher permeability is initially significantly high and is apparent only in the first few months of production. A higher permeability shortens the initial linear flow regime.

Fig. 14

Inner permeability sensitivity

The production is directly proportional to the outer permeability. The ratio of the change in production to the change in permeability is 4:5 (Fig. 15). The effect of the higher permeability is initially negligible and is apparent only after the first linear flow regime. A higher permeability shortens the transition between different flow regimes.

Fig. 15

Outer permeability sensitivity

The production is directly proportional to the porosity. The effect of higher porosity is significant after the initial flow regime. The ratio of the change in production to the change in porosity is 1:2 (Fig. 16). The duration of the flow regimes is not affected by the change in porosity.

Fig. 16

Porosity sensitivity

The production is directly proportional to the adsorption. The effect of higher adsorption is significantly high after the initial flow. The ratio of the change in production to the change in adsorption is 2:1 (Fig. 17). The duration of the flow regimes is not affected by a change in the adsorption. Previous studies showed that gas adsorption is correlated with the TOC content and maturity.

Fig. 17

Adsorption sensitivity