Review of Formation Damage Mechanisms and Acidising Treatment Design for Carbonate Reservoir Sections in the Benue Trough, Taraba State, North East Nigeria

The Benue Trough, extending across North East Nigeria into Taraba State, contains carbonate sequences associated with Cretaceous limestone and chalk formations that represent potential exploration targets for natural gas accumulations. Formation damage in carbonate reservoirs differs fundamentally from clastic reservoir damage, with dissolution-based acidising remaining the principal remediation technique. This study reviews formation damage mechanisms in carbonate reservoir sections of the Benue Trough and designs an acidising treatment protocol appropriate for the geochemical and mechanical characteristics of these formations. Core samples from two boreholes intersecting carbonate intervals in Taraba State were characterised by X-ray fluorescence for mineralogy, and porosity-permeability measurements were made before and after controlled HCl acid treatment in laboratory core flooding experiments. Acid spending simulations using the Two-Scale Continuum model predicted optimal injection rates to achieve wormhole dominant dissolution patterns. Results indicate that HCl concentrations between 15 and 20 percent at injection rates of 0.5 to 1.2 cubic centimetres per minute per centimetre squared produce the most efficient wormholing patterns in the specific calcite-dolomite compositions encountered. Retarded organic acid systems are evaluated as alternatives for deeper penetration in high-temperature intervals. The study provides an acid treatment design matrix calibrated to Benue Trough carbonate lithologies, with recommendations for spent acid disposal in environmentally sensitive riparian areas. Keywords: formation damage, acidising, carbonate reservoir, Benue Trough, Taraba State.