|Authors||M. Redburn (Newpark Drilling Fluids) | H. Dearing (Newpark Drilling Fluids) | F. Growcock (Occidental Oil and Gas Corporation)|
|Publisher||Offshore Mediterranean Conference|
|Source||Offshore Mediterranean Conference and Exhibition, 20-22 March, Ravenna, Italy|
A significant function of drilling fluids is reduction of frictional forces between the wellbore and the drill string. New techniques in drilling and completions are being used to drill horizontal wells in unconventional resources. Because these frictional forces can potentially limit the lateral length of a well, it is especially important to manage friction to avoid excessive torque and drag on the drill string. A high-performance water based fluid has been developed that reduces torque and drag to levels normally associated with non-aqueous fluids (NAFs).
A lubricity tester is often used to evaluate and predict the impact made from the use of a drilling fluid additive on friction. The most common tester, the Fann or OFITE Model 212, is normally used in a laboratory setting. This EP (Extreme Pressure) and Lubricity Tester is designed to simulate contact between a drill string and casing and consists of a rotating ring and stationary block, which are immersed in the drilling fluid. Since an exact load under wellbore conditions is hard to determine, typically fixed levels of contact forces are used.
While the EP and Lubricity Tester has been used in drilling fluid laboratories for many years, it has not been used as an instrument in the field on a regular basis until now. When the results of lubricity tests are measured and reported daily, the fluid can be modified with additives to maintain a target Coefficient of Friction, or CoF. Because fluid lubricity is affected by changing drilling fluid properties and wellbore conditions, infrequent laboratory lubricity tests provide little benefit, whereas field measurements made on a regular basis can help to ensure that the lubricity of the fluid stays on target. Regular field measurements also allow for detailed statistical analysis of the lubricity and its relationship to other fluid properties.
Controlling the drilling fluid lubricity within specified ranges and comparing the CoF to wellbore torque and drag achieves the results required of a high-performance fluid in critical applications. Post-well analysis with industry-accepted software can be used to find a corresponding wellbore friction factor on the final casing run. In this study, over 50 casing runs made with the high-performance drilling fluid were analyzed and correlated with the measured CoF. By doing so, the benefits of the high-performance water based fluid system could be quantified and its performance optimized for future applications.