By Reuters Staff 2 Min Read (Reuters) - Prominent shale investor Dan Wilks on Tuesday reported a 7.5% active stake in troubled oilfield services firm ProPetro Holding Corp through an investment vehicle, saying he may choose to push the company for a sale or other alternatives. Dan Wilks and his brother Farris Wilks made their fortune on the shale boom through a company they founded called Frac Tech Services, which provided trucks to frackers. They sold their majority stake in the company in 2011 for $3.2 billion to a consortium led by Temasek, a Singapore sovereign fund. Over the past few years, the brothers have been acquiring stakes in hard hit services firms across North America and most recently engaged in a lengthy takeover battle for Canada’s Calfrac Well Services Ltd.