Avoidance of Formation Damage by Application of Proper Drill-In Fluid (A Case Study of a Mature Field)

Abstract

Horizontal well - 1H was drilled in a mature field in Croatia with an extended open hole interval and a high differential pressure. As a result, differential sticking has occurred when drilling the horizontal section. This was the first well to be drilled in that area with application of a drill-in fluid that included specially sized calcium carbonate bridging agent with a blend of viscosifying and filtration control polymers. To identify the best drill-in fluid composition for the horizontal section, three compositions were evaluated based on fluid-loss control and plugging properties, low-shear rheology (LSRV) and formation damage potential. Introduction Recently, drill-in fluids have become more widespread in their use primarily due to the increase of horizontal and multi-lateral drilling, the increase in open hole completion, and the potential for much higher fluid production after their use. They provide a good drilling performance in horizontal wells and, when combined with open hole completion technique, maximize the well productivity. Formation damage tends to be more significant in a horizontal or in an extended-reach well for a number of reasons1. If the fluid used for drilling and/or well completion is not compatible with the reservoir rock bad formation damage may occur. Removal of damage - if possible at all - may be a costly undertaking. Preventing it by adequate drill-in fluid may be a reasonable solution. The use of such fluid may cause minimum formation damage. That can result in substantially improved production. Most reservoirs are sensitive to any fluids other than those contained in them naturally or similar to them. Contemporary drill-in fluids aim at reaching that. A variety of fluids can be used as drill-in fluids, including water-, oil- and/or synthetic-base fluids. The selection of the most appropriate drill-in fluid depends on the type of formation to be drilled and on the completion method to be applied. Some formations tolerate a wider range of drill-in fluid composition than others do. Lower-permeability sand stones and depleted or unconsolidated sandstone reservoirs do not tolerate fluid and particle invasion without suffering extensive damage. In order to drill horizontal wells adequately, the use of properly designed drilling fluid is crucial for drilling success. Not only does the drilling fluid need to be inhibitive; it must also be capable of laying down an impermeable filter cake to seal off depleted/underpressured intervals. The key how best to apply any drill-in fluid is to match the fluid with the reservoir and the completion design. Reservoir Characteristics Reservoirs A1, A2 and A3 of the studied oil and gas field represent a single hydrodynamic unit. The reservoir rock is sandstone (thin, strongly shally sandstone, laminated with non-permeable shale and sandy shale). Principal properties of the reservoir are summarized in Table 1. Laboratory Tests Drill-in Fluid Evaluation. The key for exploit the advantage offered by a horizontal well and obtain the desired performance was minimizing damage to the formation caused by drilling because of the damage due to filtrate invasion into the formation can be significant. Drill-in Fluid Evaluation. The key for exploit the advantage offered by a horizontal well and obtain the desired performance was minimizing damage to the formation caused by drilling because of the damage due to filtrate invasion into the formation can be significant.

Waste Mandarin Peel as an Eco-Friendly Water-Based Drilling Fluid Additive

“…Filtration is the process of liquid phase separation from a drilling fluid into porous formation by the influence of differential pressure. Filtration rate and filtrate volume are directly related to the drilling rate, type of formation, formation damage, and differential sticking in the area of permeable rocks [26,27]. Generally, filtration can be defined as a measure of the drilling fluid's ability to cover a permeable formation with a thin and low-permeability cake.…”

“…For a turbulent type of flow, the effective viscosity value is the same as PV, while for laminar flow, it is calculated according to Equation (7) [47]:…”

“…Drilling fluid is a complex fluid, thus its composition and properties affect the final drilling efficiency. For a successful drilling process, drilling fluid that will meet the conditions specific to each well should be selected [7]. Depending on the liquid phase, which is the basis for the preparation of this type of fluid, drilling fluid is divided into water-based, oil-based, synthetic, and special drilling fluids.…”