The Offshore Company, a Houston-based international oil and gas drilling contractor, announced that major changes in its management structure were instituted effective April 15, 1981.

F.T. Pease and G.D. Smith were promoted to senior vice presidents and given responsibility for the company's operations and sales functions. Each will assume control of one-half of the company's worldwide drilling fleet.

The company has also promoted J.T. Shelton to senior vice president with responsibility for all operations support and control functions including technical services, engineering, training and safety. All the company's financial and administrative staff will be managed by J.G. Johnson, also promoted to senior vice president. H.L. Ogden, a vice president of the company, was named general counsel.

Other management promotions include J.O. Sharon, a vice president of Offshore, who was elected president and chief operating officer of Southland Drilling Company, Offshore's newly acquired domestic land drilling subsidiary; R.L. Guidry, who was elected assistant treasurer; and P.J. Williamson, who was elected assistant general counsel. J.R. Browning has been appointed manager of contracts and sales with overall responsibility for the company's sales effort with respect to new equipment and ventures.