John D. Platt, president and chief executive officer of Geosource Inc., Houston, announced the company's board of directors has elected Harry Bridges, former president and chief executive officer of Shell Oil Company, to membership on the board. The action came after the Geosource board approved an increase in the number of directors from eight to nine.

Mr. Bridges served as president and CEO of Shell Oil from 1971 until his retirement in May of 1976. During his 39-year career with Shell, he rose from an exploration geophysicist to chief executive while serving in technical and managerial positions throughout the world in various Shell operating units and subsidiaries.