The invention concerns compounds of Formula (I)

##STR00001##

or pharmaceutically-acceptable salts thereof, wherein R.sup.1, R.sup.2 and n have any of the meanings defined hereinbefore in the description; processes for their preparation, pharmaceutical compositions containing them and their use as anti-proliferative and/or cell-killing agents.

The apparatus and method disclosed herein form closed-loop system(s) between a downhole system that includes an RSS and a surface control system, to improve stability and performance assurance of the RSS. The apparatus and method disclosed account for the actual downhole conditions experienced by the RSS, the actual positioning of the RSS, and historical performance of the surface systems such as the mud pump system, the rotary drive system, and the draw works. These closed-loop systems generate and optimize parameters or target outputs, instructions to surface systems, and instructions for the RSS itself.

The apparatus and method disclosed herein form closed-loop system(s) between a downhole system that includes an RSS and a surface control system, to improve stability and performance assurance of the RSS. The apparatus and method disclosed account for the actual downhole conditions experienced by the RSS, the actual positioning of the RSS, and historical performance of the surface systems such as the mud pump system, the rotary drive system, and the draw works. These closed-loop systems generate and optimize parameters or target outputs, instructions to surface systems, and instructions for the RSS itself.

A method for estimating a rate of penetration while drilling a subterranean wellbore includes estimating a first rate of penetration while drilling using a first measurement method, estimating a second rate of penetration while drilling using a second measurement method, and combining the first and second rates of penetration to obtain a combined rate of penetration of drilling.

A method for estimating a rate of penetration while drilling a subterranean wellbore includes estimating a first rate of penetration while drilling using a first measurement method, estimating a second rate of penetration while drilling using a second measurement method, and combining the first and second rates of penetration to obtain a combined rate of penetration of drilling.

The disclosed embodiments include systems and methods to improve downhole drilling. In one embodiment, a method to improve downhole drilling includes receiving a well plan, where the well plan is indicative of a well path to form a borehole of a hydrocarbon well is provided. The method also includes receiving measurements indicative of a previously-drilled section of the borehole. The method further includes generating, based on the measurements, a trajectory of the borehole, where the trajectory is a function of a depth. The method further includes providing the trajectory of the borehole to a Model Predictive Controller. The method further includes steering a tool towards the well path based on an output of the Model Predictive Controller.

The disclosed embodiments include systems and methods to improve downhole drilling. In one embodiment, a method to improve downhole drilling includes receiving a well plan, where the well plan is indicative of a well path to form a borehole of a hydrocarbon well is provided. The method also includes receiving measurements indicative of a previously-drilled section of the borehole. The method further includes generating, based on the measurements, a trajectory of the borehole, where the trajectory is a function of a depth. The method further includes providing the trajectory of the borehole to a Model Predictive Controller. The method further includes steering a tool towards the well path based on an output of the Model Predictive Controller.

Analysis and control of drilling mud and additives is disclosed using a mud analysis system and a mud additive system that may automatically monitor and control the drilling mud during drilling of a well. The mud analysis system may acquire measurements on a sample of the drilling mud during drilling, and may send signals indicative of the drilling mud to a steering control system enabled to control the drilling. The steering control system may receive user input or may make decisions regarding additives to be added to the drilling mud and the timing thereof. The mud additive system may be enabled to receive commands from the steering control system and mix and add additives to the drilling mud.

A retrievable whipstock assembly for a wellbore includes a whipstock including a longitudinal body and an anchor connection, a deflection surface provided on the longitudinal body with a first engagement element, and a drilling assembly including a drill housing and a second engagement element. The second engagement element is selectively extendible between a recessed position and an extended position. In the extended position the second engagement element is engageable with the first engagement element.

Methods, systems, and apparatus for imparting and limiting hypocycloidal, lateral, and torsional forces onto drill bits are provided, including hypocycloidal bearings for limiting hypocycloidal motion, lateral impulse mechanisms for imparting lateral movement to a drill bit, and torsional impulse mechanisms for imparting torsional movement to a drill bit. The methods systems, and apparatus may decrease friction, increase drilling efficiency, and provide additional benefits to drilling systems.