Rotary steering method and system for drilling borehole

Abstract

This disclosure relates to methods and systems for directional drilling. Two or more actuated members of the system simultaneously apply forces to a wellbore wall, increasing efficiency of a three members design by 90% and by 140% for a four member design. The system includes a steering head unit with elongated shape of actuated members with area of communication with drilling fluid greater 2-3 or more time of total area of conventional designs. The combination of using simultaneous force of two or more actuated members and a large area of actuated members base allows to increase the magnitude of the force impact to the wellbore surface created due to the passage of drilling fluid through the drill bit by six or more time, resulting in an opportunity to achieve high level of DLS. During proportional steering, drilling cycle is divided by sub-cycles providing smooth trajectory of a wellbore.

1 . A rotary steering system configured to control a directional orientation of a drill bit along a well trajectory into an earthen formation, the rotary steering system comprising:
 a drill bit;   a steering head connected to said drill bit and to a drill collar by an upward side, wherein said steering head includes three or more extended members, wherein two or more of the three or more extended members are configured to simultaneously apply force to a wellbore wall by using a fixed dwell angle in a range of about 120°<λ≤180°, where λ is a dwell angle, wherein an extended member of the three or more extended members is open at λ/2 degrees before an actual desired tool face orientation, and starts retraction at λ/2 degrees thereafter;   a control assembly, comprising means for determining a spatial position of the steering head by using one or more directional sensors; and   a gate for delivering a force transmitting medium to activate the three or more extended members.   
     
     
         2 . The rotary steering system of  claim 1 , wherein the gate is a rotary valve assembly comprising of an upper component and a lower component, wherein the upper component is a rotational valve with an arcuate design which incorporates an opening with an angular arc angle equal β degrees to an opening extending inwardly from periphery of the valve plate towards its center, wherein the lower component is a manifold block with at least three flow channels with openings for entering flow of pressurized drilling fluid via a drill string and passing the pressurized drilling fluid to a corresponding extended member of the three or more extended members, wherein an angular angle of the openings is equal to α degrees wherein for sum of β and α the following condition is satisfied 120°<β+α≤180°. 
     
     
         3 . The rotary steering system of  claim 2 , wherein the rotational valve includes a value shaft connected to an output shaft of a motor assembly configured to rotate the valve shaft in an opposite direction from the drill collar rotation in such a way that a center of the valve openings is predominantly pointed into a disable direction with respect to wellbore trajectory. 
     
     
         4 . The rotary steering system of  claim 3 , wherein the openings for said flow channels each include an insert made of wear-resistant material, wherein said insert is extended beyond the manifold block upward surface by about 0.2-2.4 mm, wherein a top surface of each of the inserts is in sliding contact with a flat downward surface of the rotational valve disk. 
     
     
         5 . The rotary steering system of  claim 3 , wherein the pressurized drilling fluid pressure above and below a rotational valve plate is balanced by selecting a rotational valve shaft cross-section area using equation S sh =S ch  (I−P/P dif ),
 where S sh  is a cross-section area of the rotational valve shaft, S ch  is a cross-section area of an inlet of a flow distribution channel, P is a drilling fluid pressure above and below the rotational valve plate, and P dif  is a differential pressure created by passing drilling fluid through the bit. 
 
     
     
         6 . The rotary steering system of  claim 2 , wherein said manifold block has a shape of a cylinder with a diameter substantially equal to a diameter of the a disk of the rotational valve, wherein a main portion of drilling mud flows between external surface of the manifold block and an inner surface of a steering head to the drill bit end via a drilling passage, and less than 5% from a total of the drilling mud flows going into each of the two or more openings in the manifold block, where each opening of the two or more openings is connected to actuated members and during the actuation time the drilling mud flows into the annulus through a gap between a retained chamber for an actuated member and an inner lateral surface of the actuated member. 
     
     
         7 . The rotary steering system of  claim 6 , wherein a total cross-sectional area of the gap to the annulus and the diameter of the flow channels are disposed in a such way that a pressure loss inside the actuated members does not exceed a predetermined value. 
     
     
         8 . A rotary steering system, comprising:
 a drill bit;   a steering head connected to said drill bit and to a drill collar by an upward side, wherein said steering head includes two or more extendable members, wherein each said expendable member is a pad assembly comprising:
 a pad of elongated shape in a direction of a steering head longitudinal axis, wherein an area of engagement with pressurized drilling flow is substantially equal to an area of a top cover of said pad assembly minus an area of the pad assembly cross section of lateral walls; 
 a chamber for retention of the paid; 
 a gap between an inner lateral surface of the chamber and lateral external surface of the pad, 
 a set of springs disposed to detach outer surface of a pad cover from a borehole wall after end of an activation period; 
   a control assembly comprising means of determining a spatial position of a steering head by using directional sensors; and   a fluid-metering assembly configured to selectively meter flow of a drilling fluid into fluid channels of the steering head.   
     
     
         9 . The rotary steering system of  claim 8 , wherein the pad comprises:
 a top cover;   a base plate of the top cover;   intermediate mounting angles;   a cavity between the top cover and said base plate of the top cover, wherein the top cover and the intermediate mounting angles include aligned holes through which the top cover and the intermediate mounting angles are fastened to the base plate.   
     
     
         10 . The rotary steering system of  claim 9 , wherein the base plate includes open area, wherein the set of springs passes through said open areas in the base plate and is attached to the base plate such that means for attachment are located in a space between a bottom surface of the top cover and a facing surface of the base plate, wherein opposite ends of each of the springs of the set of springs are attached to a bottom of the chamber. 
     
     
         11 . The rotary steering system of  claim 8 , wherein the fluid-metering assembly is a rotational valve assembly comprising of an upper component and a lower component, wherein the upper component is a rotational valve which is incorporated into an opening, wherein the lower component is a manifold block with at least two openings for receiving drilling flow via a drill string and passes drilling flow to the corresponding pad assembly. 
     
     
         12 . The rotary steering system of  claim 11 , wherein the upper component is located at a downward portion of the control assembly and the lower component is located inside the steering head, wherein the manifold block is held in a position such that movement is possible only along a longitudinal axis of the steering head, which is achieved by placing an upward end of the manifold block into a hole of a guide device, which is installed near the drill bit and immediately adjacent to an inner surface of steering head. 
     
     
         13 . The rotary steering system of  claim 8 , wherein middle of the steering head is located near the drill bit thread at a distance equal to half of the pad cover length plus the width of the guide device that may be as short as 2 inches. 
     
     
         14 . The rotary steering system of  claim 12 , wherein the bottom of each retaining chamber are attached to the manifold block. 
     
     
         15 . The rotary steering system of  claim 8 , wherein a compression force of each of the springs of the set of springs ensures that a volume of the drilling fluid displaced into the annulus exceeds a volume of the drilling fluid entering into the chamber due to leakage during a period of closing of a flow channel. 
     
     
         16 . A method for directional drilling a wellbore with a rotary steering system through a subterrain formation, the method comprising:
 (a) rotating a drill string with a drill bit within a wellbore;   (b) selecting a steering head with three or more extended members;   (c) providing through a flow-metering assembly means for simultaneously actuating two or more of said extended members;   (d) calculating a differential pressure resulting from passage of drilling fluid through the drill bit for different drilling fluid rates;   (e) calculating a coefficient of constructive interference due to the simultaneous impact on a wellbore wall of two or more of the extended members sufficient to create a required average force impact on the wellbore wall by choosing a dwell angle in a range of about 120 to 180 degrees for the pushing of the pressurized drilling fluid for the extended members; and   (f) determining a special position of the steering head by using one or more directional sensors.   
     
     
         17 . The method of  claim 16 , wherein each of the extended members has an elongated shape in a direction of a longitudinal axis of the steering head, allowing for an increased area of communication with pressurized drilling fluid. 
     
     
         18 . The method of  claim 17 , wherein a required average force of impact on the wellbore wall is achieved due to a multiplicative effect of constructive interference and increasing an area of contact with pressurized fluid in the extended members. 
     
     
         19 . The method of  claim 18 , wherein the flow-metering assembly is a flow rotational valve assembly comprising an upper component and a lower component, wherein the upper component is a rotational valve with an arcuate design which incorporates an opening with an angular arc angle equal α degrees, the opening extends inwardly from a periphery of a valve plate towards its center, wherein the lower component is a manifold block with at least three or more flow channels with openings for entering pressurized drilling flow via a drill string to the corresponding extended members, wherein a sum of angles for the rotational valve opening and flow channel is in a range between about 120 and 180 degrees. 
     
     
         20 . The method of  claim 16 , wherein the openings for said flow channels include inserts which are extended beyond the manifold block upward surface by 0.2-2 mm or more, allowing for a balance between drilling fluid pressure above and below the rotational valve disk and have low friction sliding contact between top surface of inserts and flat downward surface of the rotational valve disk. 
     
     
         21 . The method of  claim 17 , wherein the extended members each include pad assembles, each pad assembly comprising:
 a top cover;   a base plate;   two intermediate connecting plates that hold together the top cover and the base plate;   a free space between said two intermediate plates for fastening upper parts of retaining springs; and   a cavity between the base plate and a bottom of a retained chamber and means for fastening the bottom parts of the retaining springs to the bottom of the retained chamber.   
     
     
         22 . The method of  claim 21 , wherein a compression force of the retained rings is springs configured to displace to an annulus a predefined volume of the drilling fluid entering into the cavity inside of the pad assembly during a period of closing of the corresponding flow channel. 
     
     
         23 . The method of  claim 16 , further comprising:
 (a) obtaining a wellbore planning trajectory and a drilling plan;   (b) selecting a dog leg severity (DLS) for a current formation and calculating a steering ratio for a particular portion of a wellbore trajectory;   (c) selecting a drilling cycle time and amount of sub-cycles for a proportional steering drilling;   (d) downlinking said proportional steering parameters;   (e) drilling one drill pipe or drill stand and performing a stationary survey by using directional sensors and uplink data to the surface;   (f) comparing an actual and an assumed value of the DLS and, if a difference is above a predefined threshold, then calculating new parameters of the proportional steering and downlinking new drilling instructions.   
     
     
         24 . A method of directional drilling using a rotary steering system, the method comprising:
 independently activating a steering head with three or more independently activated extended members by using dwell angles in a range about 120°<dwell angle≤180° in order to increase impact on a wellbore wall.   
     
     
         25 . The method of  claim 24 , wherein the dwell angle is equal to about 180 degrees.