Oil-field-services companies are depleted after slashing prices and laying off workers, and their slow recovery could crimp the energy industry’s overall ability to bounce back from the oil bust. The workhorses of the energy sector, the services companies, which range from giants such as Schlumberger Ltd. SLB 0.55 % to small family-run operations, provide much of the muscle and specialty know-how needed to extract oil and gas. They pioneered the technologies that allowed producers to unlock massive volumes of oil and gas trapped in shale-rock formations, and marshal critical equipment and people to drill and pump wells from remote corners of North Dakota to platforms miles offshore. But they have borne the brunt of two years of belt-tightening in the oil patch, leaving them short on cash and manpower as prices slowly rebound and […]