A House committee chairman wants the energy secretary to explain why the head of the office handling oil price overcharge cases is being replaced.

Rep. John D. Dingell (D-Mich.), chairman of the Energy and Commerce Committee and its oversight and investigations subcommittee, wrote Energy Secretary John S. Herrington that the change "causes me to wonder whether some in the administration are once again trying to scuttle enforcement of oil overcharge cases."

The White House announced last week that President Reagan intends to nominate Chandler van Orman, deputy head of the department's Economic Regulatory Administration (ERA) since June, to take over the director's job from Marshall Staunton.

Anson Franklin, assistant secretary for congressional affairs, said yesterday that Herrington plans to respond to Dingell "in short order."

Franklin said, "Regardless of what happens to ERA, the department will still pursue these cases."

In a letter dated Nov. 4, Dingell said Staunton appeared "honest and capable and . . . has apparently had considerable success in substantially reducing the oil overcharge cases . . . generally without affording amnesty." He asked for a reply within 20 days.

In the 1970s, the ERA had 2,500 employes pursuing violations of oil price controls. The Reagan administration ended remaining controls in 1981; the office now has about 200 employes and 191 unsettled cases.

Dingell said he understood that one of the department's most controversial cases seeking recovery of an estimated $20 million from Anchor Gasoline Corp. of Tulsa, Okla., and its affiliate Canal Refining Co. of Church Point, La., had been turned over to van Orman despite "firm action" from Staunton and was now the subject of "considerable controversy," the nature of which he did not specify.

Staunton did not return a telephone call. A vice president of Anchor also did not return a call.