Application of Novel Technology Improves Drilling Performance In Multilateral Field Development Offshore West India—Reducing Risk And Increasing Production
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The operator has been active in Panna field for several years drilling a main horizontal and two laterals through a window milled in pre-existing 9–5/8″ casing. The laterals vary in length between 800m to 1600m, depending on the carbonate reservoir's constraints. However, interbedded formations with contrasting hardness had the potential to cause stick-slip and lateral vibration. Initially, the operator utilized RSS/MWD to geosteer the BHA within the target formation. However, previously chosen PDC bits caused severe lateral vibrations, stick slip and BHA whirl that resulted in multiple downhole tool failures. It appeared new PDC technology was required. An in-depth study revealed the BHA was exposed to severe stick-slip and lateral vibrations. There were also regular instances of BHA whirl and severe acceleration and deceleration caused by stick-slip. To enhance overall bit/BHA stability, a new-style 8–1/2″ PDC was implemented with innovative depth-of-cut control (DOCC) technology and enhanced stability features. BHA design was also reviewed and minor changes were implemented. The result was a significant reduction in stickslip, lateral vibration and BHA whirl. The new PDC/RSS set a new national Indian record for the longest 8–1/2" offshore section making 3956m of hole in a single run. The bit has since successfully drilled several multilateral drainholes in a single run proving the reliability of the new PDC design and enabling technology. The authors will present the vibration signature of a standard PDC versus the new one with DOCC. The authors will discuss proper RSS/PDC bit selection and demonstrate the benefit of DOCC/PDC on RSS when applied in high angle/horizontal wells. Introduction The Panna field1–3 is located in Arabian Sea about 95 km west of Mumbai, India (Figure 1). It is surrounded by other fields including Mukta, Neelam, Tapti and Bombay High. Together they constitute an important oil producing area of India. The Panna field is jointly owned by BG Exploration & Production India Limited (BGEPIL), who have a 30% holding, the Indian Government's Oil and Natural Gas Corporation Limited (ONGC) who maintain a 40% holding and Reliance Industries Limited (RIL) are partners with a 30% share. The field was discovered in 1977 and is estimated to have approximately one billion bbls of oil and 1.9 trillion cubic feet (tcf) of gas in place. Panna field produces from predominantly two carbonate reservoirs, including the upper A-zone (Oligocene) and lower B-zone (Middle Eocene). Overburden consists of argillaceous sediments of Chinchini, Tapti, Mahim and Bombay limestone followed by Alternations that lies directly on the A-zone reservoir (Figure 2). The Alternations horizon is between 70–100m thick and consists of thin interbedded shale and limestone formations of varying hardness. BGEPIL's current drilling campaign involves re-entering wells through a window milled in pre-existing 9–5/8″ casing to drill multiple fishbone laterals (Figure 3) through the reservoir section utilizing a rotary closed loop (RCLS) drilling system integrated with a resistivity, density and neutron porosity formation evaluation (FE) package (Figure 4). Application Challenges The initial horizontal wells in the Panna drilling campaign utilized steerable motors with LWD tools. However, this BHA experienced sliding difficulties that limited the extent of the horizontal reach. There were also drilling dynamics issues that caused severe tool damage on several occasions. Directional requirements/formation mineralogy while drilling the open-hole sidetrack in the 8–1/2″ horizontal section required the bit to deliver optimum dogleg severity without having an aggressive gauge as this may initiate hole spiraling and compromise wellbore quality and operational efficiency.
The operator has been active in Panna field for several years drilling a main horizontal and two laterals through a window milled in pre-existing 9–5/8″ casing. The laterals vary in length between 800m to 1600m, depending on the carbonate reservoir's constraints. However, interbedded formations with contrasting hardness had the potential to cause stick-slip and lateral vibration. Initially, the operator utilized RSS/MWD to geosteer the BHA within the target formation. However, previously chosen PDC bits caused severe lateral vibrations, stick slip and BHA whirl that resulted in multiple downhole tool failures. It appeared new PDC technology was required. An in-depth study revealed the BHA was exposed to severe stick-slip and lateral vibrations. There were also regular instances of BHA whirl and severe acceleration and deceleration caused by stick-slip. To enhance overall bit/BHA stability, a new-style 8–1/2″ PDC was implemented with innovative depth-of-cut control (DOCC) technology and enhanced stability features. BHA design was also reviewed and minor changes were implemented. The result was a significant reduction in stickslip, lateral vibration and BHA whirl. The new PDC/RSS set a new national Indian record for the longest 8–1/2" offshore section making 3956m of hole in a single run. The bit has since successfully drilled several multilateral drainholes in a single run proving the reliability of the new PDC design and enabling technology. The authors will present the vibration signature of a standard PDC versus the new one with DOCC. The authors will discuss proper RSS/PDC bit selection and demonstrate the benefit of DOCC/PDC on RSS when applied in high angle/horizontal wells. Introduction The Panna field1–3 is located in Arabian Sea about 95 km west of Mumbai, India (Figure 1). It is surrounded by other fields including Mukta, Neelam, Tapti and Bombay High. Together they constitute an important oil producing area of India. The Panna field is jointly owned by BG Exploration & Production India Limited (BGEPIL), who have a 30% holding, the Indian Government's Oil and Natural Gas Corporation Limited (ONGC) who maintain a 40% holding and Reliance Industries Limited (RIL) are partners with a 30% share. The field was discovered in 1977 and is estimated to have approximately one billion bbls of oil and 1.9 trillion cubic feet (tcf) of gas in place. Panna field produces from predominantly two carbonate reservoirs, including the upper A-zone (Oligocene) and lower B-zone (Middle Eocene). Overburden consists of argillaceous sediments of Chinchini, Tapti, Mahim and Bombay limestone followed by Alternations that lies directly on the A-zone reservoir (Figure 2). The Alternations horizon is between 70–100m thick and consists of thin interbedded shale and limestone formations of varying hardness. BGEPIL's current drilling campaign involves re-entering wells through a window milled in pre-existing 9–5/8″ casing to drill multiple fishbone laterals (Figure 3) through the reservoir section utilizing a rotary closed loop (RCLS) drilling system integrated with a resistivity, density and neutron porosity formation evaluation (FE) package (Figure 4). Application Challenges The initial horizontal wells in the Panna drilling campaign utilized steerable motors with LWD tools. However, this BHA experienced sliding difficulties that limited the extent of the horizontal reach. There were also drilling dynamics issues that caused severe tool damage on several occasions. Directional requirements/formation mineralogy while drilling the open-hole sidetrack in the 8–1/2″ horizontal section required the bit to deliver optimum dogleg severity without having an aggressive gauge as this may initiate hole spiraling and compromise wellbore quality and operational efficiency.
Troll West Oilfield Development—How a Giant Gas Field Became the Largest Oil Field in the NCS through Innovative Field and Technology Development
The Troll West Oil Field has been, and still is, developed with more than 110 horizontal sub sea wells including 53 multi lateral wells (MLT). Several of the MLT wells have over time been designed and drilled with multiple open hole sidetracks to increase drainage area for each wellhead. The Troll West Oil Field has been developed from the first test wells drilled in 1984 and 1986, with oil production on stream in 1994 and continuous development still ongoing. The commercial oil reserves on the field have gone from 0 in 1986 to more than 1,400 million barrels today. To be able to achieve this tremendous economical upside, the thin oil rim has been developed through sub sea development and extensive horizontal drilling enhancement. The latest development is through extensive use of multilateral drilling and wells containing up to 7 horizontal branches. The process of drilling the MLT wells and the benefit and risk evaluation for the MLT process is discussed and illustrated in this paper. The additional drainage area gained from open hole sidetracks are delivering additional production to each well head. The unique method used for the open hole sidetracks has proved to be a low risk strategy and highly economical way to get access to additional reserves thus reducing the need for additional sub-sea templates on the field. This paper shows how the field and technology development has evolved over the last two decades and plans going forward to continue strengthening the Troll West Oil Field production for another 15 years+ prior to the gas drainage. The upcoming technologies are incorporating both drilling and Logging-While-Drilling technologies to enhance the understanding of the mechanics behind the field development.
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