Mud-Induced Formation Damage in Carbonate Reservoirs: Consequences on Productivity of Open-Hole Horizontal Wells

Abstract

Abstract An integrated approach including laboratory testing and numerical modeling was used in a study focused on mud-induced formation damage in carbonate open-hole horizontal wells, related to a field application in Saudi Arabia. This approach incorporates (1) evaluation of damage from laboratory flow experiments; (2) interpretation of flow testing results by two-phase flow modeling, and (3) integration of the physical data describing the formation damage into a numerical near-wellbore model for the evaluation of skin value and well productivity. In the laboratory investigation, drilling and clean-up fluids were applied to two different reservoir core samples representing two classes of permeability. Two cleaning fluids were compared: a conventional mild acid wash and a new product system comprising a retarded acid and an enzyme breaker. Although laboratory testing is helpful for the selection of drilling and clean-up fluid, it cannot be directly used to evaluate well performance. Hence, a numerical model, which takes into account near-wellbore formation damage mechanism and laboratory testing data, is used to estimate potential productivity loss. The modeling of the lab results shows that the heterogeneity of the cores has a determinant effect on the flow parameters (second drainage). This interpretation of the lab results is fundamental for the well modeling. Well productivity after drilling was evaluated with a dedicated software for Modeling Inflow Performance (MIP). The improvements brought by the new cleaning fluid were evaluated by both laboratory experiments and numerical simulations. The results obtained show comparable skin values between model prediction and field data.