Credit Suisse has lifted its target price for Royal Dutch Shell, saying that the oil major's recent first-half results showed "encouraging signs" and that the business is "firing ahead".The bank said that Shell is its "top pick" among the major European oil and gas producers, reiterating an 'outperform' rating for the shares.Excluding working capital movements, operating cash flow (OCF) totaled around $24bn for the first six months of 2014. Credit Suisse said this "easily exceed[ed] market expectations - a royal performance amongst the global majors in 1H14"."We have previously said the existing base can deliver potentially a strong OCF uplift and that our estimates may prove too conservative. More upside is likely forthcoming."Credit Suisse said it has lifted its OCF estimates for Shell, which takes its target price for the shares from 2,600p to 2,700p."RDS is indeed squeezing out more from the current asset base, and as some of the mega projects come on stream over the medium term with a growing share of long life assets, cash flow will grow further and capex intensity should fall."Meanwhile, the bank said that Shell's investment approach, resource depth, liquefied natural gas portfolio and its ability to cover spending and a growing dividend "will translate into superior shareholder returns".