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One issue of great concern for shale gas producers is price volatility. The price of heating value and of NGLs has fluctuated significantly over the last 15 years [33]. The average and standard deviation for NGL and heating value price data were determined assuming a normal distribution (see Table 2.10) [25].

Table 2.10 Maximum, minimum, average, and standard deviation for price data.

	Maximum	Minimum	Average	Standard deviation
Heating value ($/MMBtu)	US$13.42	US$1.72	US$4.40	US$2.22
Ethane ($/gal)	US$1.39	US$0.14	US$0.43	US$0.27
Propane ($/gal)	US$1.89	US$0.36	US$0.97	US$0.37
n‐Butane ($/gal)	US$2.31	US$0.49	US$1.26	US$0.47

A Monte Carlo simulation with 10 000 iterations was performed to find the probability of not being profitable for the base case (when ROI < 10%). Variables were set to be distributed normally in the simulation program. The probability of losing money was about 36%. The average ROI was about 59%; however the standard deviation from the Monte Carlo was approximately 135%. Clearly the shale gas processing business is potentially very profitable, but also very risky. The measured contributions to variance on ROI are shown in Figure 2.12.

Figure 2.12 Measured contributions to variance on ROI for the inputs.

By far the biggest contributor is the heating value, which affects both raw material cost and the sales gas price. This makes sense because methane is the predominant component for this feed (77.78 mol%).