Lower oil prices overshadowed a positive development. Shares of Devon Energy (DVN 3.19%) fell 12.6% in September, according to data provided by S&P Global Market Intelligence. The culprit was lower oil prices. That offset the positive effect of closing a needle-moving acquisition. Down despite a big deal Oil prices were under pressure again last month. WTI, the main U.S. oil price benchmark, fell another 7.3% in September, closing the month at around $68 per barrel. It has now declined by 16.4% over the pas ...