Accurate and frequent mud checking is critical to optimum well construction. Proper assessment and management of drilling fluid properties such as density and rheology maintain the primary well control barrier and optimize fluid hydraulics and hole cleaning ability. However, a full mud check while drilling is typically done only once or twice a day. Moreover, the measurements are performed using antiquated equipment, with data quality and reliability that are highly dependent on the practicing mud engineer. Automated, continuous and practical drilling fluid monitoring is therefore needed.
In this paper, we introduce an automated mud skid unit (MSU) which performs continuous drilling fluid sampling and measurements at variable temperatures. The unit is able to provide the non-Newtonian rheological constants characterizing a Yield-Power Law (YPL) fluid as well as the real-time friction factor and critical Reynolds number using a pipe-viscometer measurement approach. Other important fluid properties such as pressurized-density, oil/water ratio and temperature are provided using high-quality in-line sensors. The unit is controlled by a programmable logic controller (PLC) coupled with a Linux operating system for data analysis. The system is able to send real-time data to WITSML data servers and provide detailed mud reports to engineers working either on-site or remotely.
The MSU was deployed in the Permian basin by an independent operator for automated mud monitoring during unconventional shale drilling operations. Rheology, density and phase content measurements were compared with conventional mud reports provided by the on-site mud engineer. Excellent accuracy was observed in mud rheology tests. The pressurized mud-density measurements provided by the MSU proved to be more accurate than non-pressurized mud balance measurements which were affected by mud aeration. Moreover, the MSU provided mud check data 25 times more frequent than those generated by the mud engineer at temperatures of 50°C and 65.5°C. Drilling fluid related issues such as chemical over-treatment as well as sudden changes in mud density, rheology and oil/water ratio were reported immediately to the drilling crew. This paper provides details about the measurement technology as well as the results from the field deployment of the MSU.
Rostagno, Ian (The University of Texas at Austin) | Yi, Michael (The University of Texas at Austin) | Ashok, Pradeepkumar (The University of Texas at Austin) | van Oort, Eric (The University of Texas at Austin) | Potash, Ben (Pioneer Natural Resources) | Mullin, Chris (Pioneer Natural Resources)
Pipe rocking is a process used during slide drilling to reduce friction between the drillstring and the wellbore. Pipe rocking is widely practiced in unconventional drilling operations, either conducted manually or through an automated system. Often times, the rocking regime adopted in the field is based only on experience and may not be at optimum, leading to higher friction with poor force transfer to the bit and reduced rate of penetration. In addition, non-optimum pipe rocking can lead to accidental connection back-offs and poor toolface control.
This paper introduces the first rocking simulator based on real time and contextual data to provide the driller with a robust recommendation of the optimum rocking regime, i.e. guidance on the optimum number of forward and reverse wraps in the drillstring and the time period in which to generate these wraps.
A model was developed to optimize the pipe rocking regime, determined by the specifics of rotating the drillstring at a certain RPM for a certain number of turns in forward and backwards directions. The objective was to keep the directional toolface constant while optimally reducing sliding friction between the drillstring and the wellbore. A torque and drag model was used to obtain the frictional forces between the drillstring and the wellbore. Drillstring dynamics was then simulated using a torsional damped wave equation applying finite difference approximations. Finally, the angular deformation as a function of time and measured depth for each drillstring element was calculated.
Static friction is an important performance limiter when slide drilling with a downhole motor. Pipe rocking can be used as a low-cost technique to break the static friction in a section of the well and thereby reduce its negative effect. Pipe rocking simulation was used to find the rocking regime that maximizes the section of the string under conditions of dynamic friction, without losing toolface control. The torsional damped wave equation was used as a drillstring dynamics model because it successfully accounts for the surface rotational energy that is dissipated as elastic energy stored in the drill pipe and friction against the wellbore. Simulations resulted in recommendations to the directional driller on the optimum pipe rocking regime to adopt. The methodology was applied on a historical data set consisting of more than 100 US land wells. It was observed that improper pipe rocking could lead to back-off events, poor toolface control and reduced force transfer to the bit. By minimizing friction, longer horizontal sections and reductions in tortuosity can be achieved. An advisory software program was developed to guide directional drillers on favorable pipe rocking regimes based on contextual and real time data.