Oil prices continued their recent upward trajectory in Monday business following a potentially game-changing accord between Saudi Arabia and Russia, news that saw Brent come within a whisker of the $50 per barrel marker once again.

The news couldn’t prevent two London-listed oilies sinking after the release of their latest operating updates, however.

Alaska-focused 88 Energy (LSE: 88E) was recently trading 18% lower from Friday’s close, while Pantheon Resources (LSE: PANR) collapsed 39% from the previous session.

Texan troubles

Pantheon announced that work at its VOBM2 well in Polk County, East Texas had ceased thanks to difficulties drilling through the sandstone at the Eagle Ford project.

The company advised that “drilling of the horizontal section of the well was delayed by a series of equipment failures, causing the operator to replace contractors a number of times.” Problems were encountered due to the rock’s “abnormally abrasive characteristics,” Pantheon advised, which saw drilling halt to just two feet per hour at times.

The well has now been plugged, the driller noted, and the drilling rig moved to Pantheon’s VOBM3 well. However, the oil play plans to return to VOBM2 and to drill vertically once work on the latter is completed.

Indeed, Pantheon remains bullish on the commercial viability of VOBM2, commenting that “the well has encountered significant hydrocarbons in the objective horizon with natural gas being flared for several days, confirming the presence of a productive reservoir consistent with pre-drill expectations.”

Cold as ice

88 Energy, meanwhile, retreated further from recent four-month peaks after finalising drilling plans at its Icewine #2 asset in United States’ frostier parts.

88 Energy advised, after consultation with its partner Burgundy Xploration, that Icewine #2 would now feature “a vertical well with a multi stage stimulation” instead of the initially-proposed lateral well.

The move will cut costs at the project by approximately $5m, 88 Energy advised, meaning that the company can now fully fund the project from existing cash reserves. The new plan also reduces risk as a vertical model is far less complex than a laterally-oriented one.

Risky business

Share price volatility is par for the course for those investing in oil and gas explorers.

88 Energy itself has seen its value explode in 2016 after the potential payloads at Icewine #2 became apparent. Indeed, the share is still up more than 550% since the turn of the year.

But the unpredictable nature of fossil fuel delivery and unexpected changes to production plans can easily send share prices sinking again, particularly as many operators carry cash-strapped balance sheets and don’t generate revenues to help offset their hulking capex costs.

The oil sector remains a risk-heavy sector, anyway, with bursting crude inventories and a lack of orchestrated action to cut supply threatening to keep fuel prices under pressure. Indeed, I reckon the huge economic and political considerations surrounding possible reductions mean that investors should read little into Riyadh’s and Moscow’s plans to establish a task force to battle the market imbalance.

I think investors should give Pantheon Resources and 88 Energy a wide berth given these factors.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.