The investigations, conducted by many companies, show that a long gauge PDC bits, which are used during operations with "point-the-bit" Rotary Steerable Systems (RSS), allows for mitigating the bit vibrations and improve steerability. But in this paper, we shall present the usage of the short gauge PDC bits when drilling with this type of RSS in a pay zone, which is characterized by hard streaks. More tight shaled-out interlayers were encountered in pay zone when developing a peripherical part of Verkhnechonskoye field. On the boundary of the rocks of different hardness a number of formation "pushes" (short intervals with a sharp change of the inclination) increased significantly. A continuous operation in the formation "push" intervals resulted in downhole equipment damages. When conducting kick-off operations in an open hole in multilateral wells with the use of "point-the-bit" RSS and the long gauge bits a quantity of failures reached 60 %. For that reason, it was necessary to kick off using a BHA with a downhole motor; but in this case additional runs are required. A hypothesis was made that the usage of short gauge PDC bits will help to promptly correct the wellbore trajectory when formation "push" occurs, as well as allow for drilling a few laterals over one run. Deviation from the standard design made it possible to reduce a number of runs when drilling multilateral wells, increase an average rate of penetration and significantly reduce frequency of Dogleg Severity exceedance events when passing through hard streaks.
Vostochno-Messoyakhskoye and Zapadno-Messoyakhskoye fields are the northernmost of the known onshore oil fields in Russia. Under severe climate and geological conditions in the field, an operator planned initially to construct horizontal wells with sidetracks with the use of fishbone drilling. This paper describes the results of construction of four fishbone wells. A comparative analysis of horizontal sidetracks as well as different downhole conditions and their impact on performance are discussed. Recommendations on effective performance of works are given. The technology of sidetracking in open hole with a rotary steerable system (RSS) was tried while drilling four wells. Fourteen sidetracks of different complexity were drilled: the distance from a casing shoe to a kickoff point (KOP) varied from 50 to 720 m; in this case the sidetrack intervals were affected by formations of different densities. The distinctive features of each of the wells are taken into account in the analysis: a number of horizontal wellbores—from 3 to 5, and a total length of the laterals—from 1980 to 3544 m. An accumulated experience made it possible to compare the sidetracking conditions and results against each other as well as make a list of practical guidelines for drilling similar wells in future. Based on performance results, the optimal conditions for sidetracking with an RSS were determined under geological conditions imposed at Vostochno-Messoyakhskoye field. The experience has shown that in case a sidetrack interval falls on dense rocks, then the duration of work increases three/fourfold. In this context, 3 levels of sidetracking difficulty were identified on the basis of the rock density. Individual recommendations related to drilling process were compiled for each level. Geosteering in mother bore plays an important role in locating a KOP. Interpretation of LWD data in real time allows identifying the level of difficulty for the upcoming sidetrack and locating a proper KOP for the next sidetrack. Apart from that, the requirements for the sidetrack interval were drawn up. It is necessary to build a tangent section in the main hole, which matches the bottomhole assembly (BHA) length. A build up interval ("ramp up") should follow immediately after the tangent section, where sidetracking is to be performed. Provided that the recommended conditions are met, it is possible to drill several horizontal sidetracks over one run, resulting in reduction of well construction time. Based on the operator company’s estimates, the fishbone drilling application made it possible to increase an initial oil production rate by 40% in average, versus conventional horizontal wells. Due to RSS usage during sidetracking and drilling horizontal holes, an overall length of horizontal sections of four wells totaled 10 kilometers (horizontal section of a conventional well is about 1000 m). After testing under challenging conditions of Vostochno-Messoyakhskoye field the fishbone drilling is ready to be applied in other regions as well.
Rotary Steerable Systems (RSS) are, in general, more efficient versus Positive Displacement Motors (PDM) when drilling the wells under complicated geological conditions. Thousands of operations, performed all over the world, clearly confirm this statement (Wardana, R, 2019). However, this paper will demonstrate that there are geological features where the main advantage of RSS – drilling with constant rotation – is not efficient and may result in emergency situations. Specifically, under such geological conditions it is necessary to drill in Tazovskoye field which is developed by extended reach horizontal and multilateral wells. This paper will cover integrated engineering solutions, which made it possible to overcome geological challenges to reduce the costs of drilling extended reach multilateral wells by a deliberate engineered change from RSS to PDM application. The approach was confirmed in 11 multilateral wells, drilled with the use of PDM. In this case the length of each horizontal hole totaled 2000 meters and more. An all-time record was achieved in Russia in terms of the length of horizontal wells, drilled with PDM motors without using oil-based mud: a horizontal section 2,520 meters in length with DDI – 6.72, ERD – 2.67 was drilled.
The pressing challenge is the abnormally rapid wear of well logging equipment and drilling tools when drilling wells in pay zone of Chayandinskoye field. Wear-out of BHA stabilizers within one run makes directional drilling inefficient and results in additional trips to replace equipment. Wear-out of drill pipes results in emergencies risk increase. To prevent such incidents the necessity arises to conduct an unscheduled inspection, reject and replace drilling tools. All these conditions entail increase in drilling time and decline in profitability. Problem analysis and expert review was made by drilling optimization specialists from DD Contractor jointly with the experts from R&D Center and Operator Company. This paper discusses how cooperation of the engineers from three companies as well as a particular approach to incident investigation and drilling engineering made it possible to identify the most critical factors, which contribute to a standard BHA wear, to work out measures to prevent similar situations in future and select an alternative BHA. The gained experience has been successfully disseminated to the other wells in Chayandinskoye field and other fields in Eastern Siberia; and the incident investigation methods and drilling engineering procedures are effectively applied under the other projects.
Multilateral drilling technology offers a highly effective method of enhanced oil recovery in fields characterized by complicated geological structure. This paper describes the analysis of sidetracks in an open hole by annular ledge formation with the use of a downhole motor in multilateral wells in Vostochno-Messoyakhskoye field. Since May 2018, more than 130 sidetracks have been drilled in Vostochno-Messoyakhskoye field with the use of bottomhole assembly (BHA) with a downhole motor in open hole by annular ledge formation. The fundamental difference between this method and conventional sidetracking with a downhole motor is that during sidetracking the entire drill string constantly rotates, rather than just bit rotation produced by downhole motor operation. In the process of technology introduction a comparison was made on how different downhole and geological conditions influence the time and performance results. The technology introduction resulted in the sidetracking time reduction from 9 hours to just 3 to 4 hours. A number of additional advantages of sidetracking with annular ledge formation were confirmed in the process of operations: The constant rotation of the drill string enables smooth weight transfer to the bit smooth, without failures. This contributes to effective and uniform ledge formation. Such sidetracking can be carried out at an extended length of open hole when it is difficult to ensure a free movement of the BHA which is necessary of conventional sidetracking. Constant rotation mitigates the risk of differential sticking. More favorable conditions are created for BHA movement in an interval of the holes diversion and subsequently for liner running in. It is possible to sidetrack with the use of a stiff BHA including a complete set of logging tools. In case of conventional sidetracking, it is preferable to use a short and flexible BHA. The experience gained in Vostochno-Messoyakhskoye field can be extrapolate to other fields where multilateral wells are drilled with annular ledge formation.
This paper describes the basics of the Targeted Bit Speed (TBS) technology and results of its application during construction of a group of wells at Urengoyskoe field located in Yamal-Nenets Autonomous Area, Russia. It highlights the advantages of TBS technology as compared to drilling with conventional BHA with a hydraulic drilling motor. It also compares various BHA configurations incorporating the TBS system. The Targeted Bit Speed technology is designed to improve well drilling efficiency. The TBS technology is based on a conventional bent-housing positive displacement motor (PDM) with measurement-while-drilling (MWD) tools. TBS technology delivers the same advantages as rotary-steerable systems enabling full 3D directional control with continuous drillstring rotation. In those cases when the required dogleg severity cannot be achieved with TBS technology, the system's operation can be suspended without retrieving the BHA to the surface with further directional drilling by conventional PDM orientation method. This paper describes the results of well construction at Urengoyskoe field, where the TBS technology was used by the operator to drill S-shaped wells with a horizontal displacement of over 1,000m. This paper focuses on directional control improvements, increased rate of penetration (ROP) and rotary drilling share achieved by the new system. Information provided in the paper applies to the first wells drilled in West Siberia by the TBS method.
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