That's good attempt at reasoning, but it's incorrect.
Oil and gas industry is stable and established industry where the earnings and dividend yield makes the return for the investment. The stock prices are in long term decline. They are not growth stocks. If P/E drops because divestment and earnings stay the same, it will generate extra ROI for investors.
To get you into the same page, consider BP and Royal Dutch Shell
Company: BP
dividend yield: 6% (2018),
P/E : 14.67,
10y stock price : -46%
Company: Royal Dutch Shell (RDS)
dividend yield: 6% (2018),
P/E : 11.70,
10y stock price : -30%
SP500 price index is up 114% during the same period.