Evolution Securities has downgraded its rating on West Africa-focused oil and gas exploration group BowLeven from buy to neutral, saying that the latest results from Sapele-3 well "leaves more questions than answers".The firm announced on Thursday that the well, located off the coast of Cameroon, found 8m of net hydrocarbon pay of which 6m were located in reservoir sands with good porosity and permeability. However, Evolution notes that "only mud log analysis and gas chromatography were used to indicate that the sands are likely to be oil bearing."Analyst Richard Griffith says that this is "far from conclusive" and investors will not know the well's true potential until the appraisal programme in 2012. The broker cuts its target price from 190p to just 80p and downgrades but notes that this is more to do with timing issues rather than potential.By 10:04, shares were trading down 7.43% to 68.5p.BC