OIL AND GAS [ FILED ] * FIELD * CHEMICALS FOR USE IN AND ANCILLIARY TO OIL AND GAS EXPLORATION, DEVELOPMENT, PRODUCTION, AND TRANSPORTATION; CHEMICALS FOR CLARIFICATION OR VISCOSITY CONTROL OF FLUIDS USED IN OIL AND GAS WELLS AND RESERVOIRS AND CRUDE OIL; CHEMICALS FOR THE PROTECTION OF OIL RESERVOIRS AND EQUIPMENT FROM DAMAGE; CHEMICALS FOR MAINTAINING THE FLOW OF OIL IN OIL WELLS ; DRILLING MUDS AND INGREDIENTS THEREOF; CHEMICALS FOR USE IN CEMENTING OIL AND GAS WELLS; CHEMICALS FOR COMPLET...