El Paso Energy Co., Houston, and Sonat Inc., Birmingham, Ala., are in the process of merging their defined benefit plans following regulatory approval of El Pasos acquisition of Sonat. Eddie Ammons, principal-benefits finance, for El Paso, said that investment consultant Mercer will begin an asset-liability study of the combined $1.2 billion pension plan. For now, all of Sonats managers remain and have switched over their account records to Deutsche Bank, El Pasos custodian. Barclays Global Investors manages four index funds for Sonats $616 million pension fund and Frank Russell manages a real estate portfolio, Mr. Ammons said. According to the 1999 Money Market Directory, the asset allocation of the fund was: 32% domestic bonds; 6% small-cap equity; 16% growth equity; 16% value equity; 17% indexed equity; 1% real estate equity; 11% international equity; and 1% emerging markets equity. At El Paso, the asset allocation mix is 60% equity and 40% bonds for the $600 million fund. J.P. Morgan manages a domestic bond fund. Templeton and Sanford C. Bernstein manage international equities. Alliance; Sanford C. Bernstein; Geewax, Terker; BlackRock; and Schmeidler manage domestic equities. Mr. Ammons expects the study and any changes in money managers to be complete by the end of the second quarter.