Women with overweight or obesity (OWOB) have an increased risk of cesarean birth, preterm birth (PTB), and high birth weight infants. Although regular exercise decreases this risk in healthy weight women, these associations have not been explored in OWOB. Women were randomized at 13–16 weeks’ gestation to 150-min of moderate-intensity exercise (n = 131) or non-exercising control (n = 61). Delivery mode, gestational age (GA), and birth weight (BW) were obtained via electronic health records. Pregnant exercisers had no differences in risk of cesarean birth, PTB, or BW compared to control participants. OWOB exercisers had higher rates of cesarean birth (27.1% vs. 11.1%), trends of higher PTB (15.3% vs. 5.6%), but normal weight babies relative to normal weight exercisers. Controlling for race and body mass index (BMI), maternal exercise reduced the relative risk (RR) for cesarean birth from 1.63 to 1.43. Cesarean births predicted by pre-pregnancy BMI and fitness level, whereas BW was predicted by race, gestational weight gain (GWG), pre-pregnancy fitness level, and exercise level. Cesarean birth was predicted by pre-pregnancy BMI and fitness level, while maternal exercise reduced the magnitudes of the relative risks of cesarean birth. Maternal exercise, pre-pregnancy fitness level, and GWG predict neonatal BW.Trial Registration: Influence of Maternal Exercise on Infant Skeletal Muscle and Metabolomics-#NCT03838146, 12/02/2019, https://register.clinicaltrials.gov/prs/app/template/EditRecord.vm?epmode=Edit&listmode=Edit&uid=U0003Z0X&ts=8&sid=S0008FWJ&cx=77ud1i.

This paper discusses the development, testing and optimization of a rotary steerable system (RSS) developed specifically to address the challenges around drilling wells in unconventional reservoirs in North America. As with offshore areas, rotary steerable drilling technology has rapidly gained acceptance for onshore use because of its clear advantages in directional control, wellbore placement and lateral reach, while matching or exceeding the drilling performance of conventional systems. The further growth of RSS into the drilling of unconventional reservoirs has been limited by the build-rate (BUR) capabilities of established RSS that prevent operators from successfully drilling curve and lateral sections in one run. In recent years, service companies have worked to improve the capabilities of rotary steerable drilling systems to meet the specific needs of drilling horizontal wells in unconventional oil and gas reservoirs. Due to lease spacing and limited vertical depths to achieve horizontal orientation, greater buildup rates (BUR) are required to maximize the lateral lengths in the reservoir. In addition to developing higher doglegs in the curve, the system should also enable lateral control to minimize tortuosity, facilitate easy casing running and optimize successful multistage fracturing. The authors outline how specific challenges, such as reduction in drilling time, improved wellbore placement, and more efficient completion and fracturing operations are addressed by the introduction of the new system. Included in this paper is a description of how the bottomhole assembly (BHA) and drill-bit properties are matched and optimized to deliver best directional control and drilling performance, according to formation characteristics in the Granite Wash play in the central USA. Explanations detail how the new system capabilities expand the possibilities to develop reservoirs using pad drilling, the use of more complex well profiles and real-time reservoir navigation, leading to increased hydrocarbon production.

Technology Update A combination of new drill-bit technology and new operational practices has enabled operator Marathon Oil to use polycrystalline-diamond-compact (PDC) drill bits, and reduce drilling time by 24%, on wells in a part of the Anadarko basin where abrasive conditions at shallow depths previously have required the use of roller-cone bits. Much of the Anadarko basin is dominated by PDC-bit drilling. However, in the southwest Canute area of Washita County, Oklahoma, the highly abrasive Granite Wash formation is encountered at depths of 5,000−6,000 ft, compared with its more typical 11,000-ft point of emergence in most of the Anadarko basin. In the deep Anadarko, of which the southwest Canute area is a part, exploratory wells are drilled either to approximately 13,500 ft to produce the Atoka Wash and Red Fork sands or to approximately 17,500 ft to pro-duce the Morrow sands. The surface string in either type of well is set in or below the Brown dolomite formation (≈3,500−4,500 ft). The lithology below the surface casing consists of a long sequence of sand/shale with interbedded granite wash. This gives way to more-consolidated sand intervals and granite-wash formations, a transition often marked by the showing of the Tonkawa and Prue sands at approximately 9,000 and 11,000 ft, respectively. In drilling Atoka Wash/Red Fork wells in the southwest Canute area, the operator set a goal of reaching the Prue sands by use of two PDC bits, eliminating the use of three to eight roller-cone bits that previously would have been required. Aggressive drilling parameters typically reserved for roller-cone bits, employing high weight on bit (WOB) and low revolutions per minute (rev/min), were combined with innovative PDC-bit frames, designed to increase the load/cutter ratio, and with new cutter technology to enable the operator to achieve the goal. A depth of 10,700 ft was reached with two PDC bits, and cost savings of approximately USD 200,000 were realized. Well Plan For the operator, a typical Atoka Wash/Red Fork well involves a 12.25-in. section drilled into the Brown dolomite and a 7.875-in. section then drilled to total depth (TD). For the 12.25-in. section, casing points differ according to TD. Typically, 9.625-in. casing is set at ≈3,500 ft. The 12.25-in. interval is easily drilled with a single PDC bit. A 7.875-in. hole is drilled below the 9.625-in. casing and extends to TD. Historically, this interval has been drilled with multiple IADC 5–2–7 or 5–3–7 roller-cone bits. More recently, the use of PDC bits at drillout has become common. However, the ability to make the interval to the Prue sands has proved very elusive.

The formation in Hemphill County, Texas and surrounding areas presents a number of challenges when drilling build section from a vertical pilot hole to form a horizontal lateral in the productive zone. The formation is hard and abrasive and it is difficult to anticipate rock properties downhole from one well to the next. The erratic nature of the formation results in unpredictable performance by the drill bit and steerable drilling assembly particularly in the build section of the curve. In many cases, the target build rates are not achieved forcing unnecessary multiple trips resulting in cost overruns. To remedy the issue, a single trip drilling system was developed to provide a reliable kick-off setting leading to the designated landing point for the lateral. From the bottom up, the drilling system consists of a hydraulically set anchor, an integral deflector, a TCI rock bit mechanically attached to the top of the deflector, a positive displacement motor and measurement tools. The integral deflector provides a dependable kick-off point and a firm beginning in initiating the build section without having to rely on a cement plug or conventional tools requiring multiple trips. The procedure includes positioning the drilling system in the pilot hole at kick-off point, orienting the deflector face with MWD in a desired direction, installing the deflector by hydraulically setting the anchor, disengaging the BHA from the deflector and commencing drilling operations. All of these steps take place in a single downhole trip. Once the rock bit and the motor assembly pass the deflector, the sliding and rotating phase efficiently achieves the target build rate. The authors will describe the system components and the running procedure. They will also discuss system performance in the Hemphill County application along with realized benefits to the operator, lessons learned and planned improvements.