|Authors||M. Winsor (Indigo Minerals) | H. Dearing (Newpark Drilling Fluids) | M. Dixon (Newpark Drilling Fluids) | J. Shipman (Newpark Drilling Fluids)|
|Publisher||Offshore Mediterranean Conference|
|Source||Offshore Mediterranean Conference and Exhibition, 25-27 March, Ravenna, Italy|
For many years one of the primary natural gas exploration and production targets in East Texas and West Lousiana has been the Cotton Valley (CV) Sands and associated subsections. The advent of new and successful technology for drilling horizontal wells have increased the return on investment to advantageous levels for this play. The Cotton Valley is a very abrasive, consolidated Jurassic-Cretaceous sandstone. When non-aqueous fluids (NAF) or conventional water-based fluid (WBF) systems are used in horizontal wells in this formation, abrasiveness combined with directional tortuosity and horizontal lateral lengths cause rates of penetration (ROPs) to suffer while torque and drag values increase to the point where drilling cannot be continued. The utilization of a high-performance water-based fluid (HP-WBF) system proves vital in meeting interval objectives while remaining cost-effective and environmentally friendly.
Primary fluid objectives in horizontal wells are typically very similar: help to maximize ROP, decrease torque and drag, stabilize the wellbore, and enhance wellbore cleaning efficiency. In an effort to improve drilling fluid effectiveness while maintaining consistent ROPs and manageable torque and drag values a number of fluid additives have been field tested in the CV horizontal wells with the goal of decreasing frictional forces. Examples include refined oil, sulfonated asphalts, graphite, and fine beads. All of these additions yield varying, inconsistent results. Using a newly developed high-performance fluid system, ROPs increase 20-50% as torque values decrease 20-50% simultaneously. The results using this systems approach show consistency, repeatability, and have proven to be cost effective.
Key factors influencing the necessity of a carefully and custom designed drilling fluid are hole size, casing design, drill string, bottom hole assembly, bit selection, and drilling fluid properties. The combined components of the well design help identify tangible measures of success. Average daily ROP and on-bottom torque are two drilling parameters identified as key performance indicators. Therefore, over the course of a given length of time ROP, torque values and other properties are monitored and recorded. After compiling and analyzing this the effectiveness of a high-performance fluid system can be determined and subsequently quantified. A case history analysis of over 30 horizontal Cotton Valley wells utilizing a high-performance fluid provides the basis for demonstrating the advantages and therefore the cost effectiveness of using this new fluid technology.