Drilling/Production

Sakhalin Energy Investment Co. has awarded Swaco, a division of M-I, a $10-million contract to provide solids control, cuttings re-injection, mud mixing, and bulk handling systems for the Sakhalin II project offshore the Sakhalin Islands.

Frank Hartley • Houston

Sakhalin development

Sakhalin Energy Investment Co. has awarded Swaco, a division of M-I, a $10-million contract to provide solids control, cuttings re-injection, mud mixing, and bulk handling systems for the Sakhalin II project offshore the Sakhalin Islands.

The project is designed to develop the Piltun-Astokhskoye and Lunskoye oil and gas fields 20 km east of Sakhalin Island. The development includes the construction of two platforms, one for each field.

The latest technology will employ programmable logic control software to control the systems. Installation of the equipment will be undertaken in 2004-2005 and is expected to be operational by 2006-2007. Production is expected to go online in 2007.

Shell, Mitsubishi, and Mitsui established SEIC to develop the Sakhalin II project in the Commonwealth of Independent States.

The operation is based on a zero-discharge policy, employing the latest generation of waste containment, treatment, and disposal technologies.

New rotary steerable system

Norsk Hydro selected a rotary steerable system to drill an openhole sidetrack in the A-10BY3H well, on the Njord platform, north of the North Sea's Norwegian sector (Norske Havet). The overall objective of the well was to improve oil recovery from the central area segments of the field development via drilling two multilaterals.

This central area of the Njord field is highly faulted with poor lateral connectivity and high geological uncertainty. The reservoir sections are typically undulating (up to sinusoidal) to account for their faulted nature. Certain compartments of the reservoir are highly abrasive while others can be unstable, presenting mechanical sticking problems. Unstable coal stringers are also evident in many reservoir compartments.

The Schlumberger PowerDrive Xceed system performed the sidetrack from openhole at 91° inclination. The plan called for a drop in inclination from 91° to 88.5°, while turning from an azimuth of 179° to 170°. The section was drilled from openhole sidetrack to total depth in one run, an accomplishment not previously achieved in this field.

Developed especially for harsh environments, this system is a fully rotating tool with a totally enclosed internal steering mechanism, which is designed to provide a high degree of accuracy and reliability in challenging applications where externally steered mechanisms reach their performance limits. A unique attribute of this rotary steerable system is full rotation of the entire drill string, ensuring optimization of the overall drilling process.

The system's directional drilling tendency is controlled through traditional three-point contact with the wellbore. This three-touch point system has only rotating elements in contact with the wellbore, which Schlumberger says provides better hole cleaning and lower equivalent circulating densities, as well as less exposure to differential sticking that occurs from static elements in contact with the formation. Its minimal dependence on the borehole wall makes the tool less susceptible to wear in abrasive formations, the company says.

The rotary steerable system's relative independence from formation influences enables, in addition to openhole sidetracks, doglegs to be drilled and steered in challenging applications with great reliability and at high build rates, the company says. For the Norsk Hydro well, the tool showed an extrapolated dogleg capability of up to 10°/30 m.

According to the company, the use of real-time vision density images enabled the well path's geosteering, thus realizing three times more producible reservoir than any previous single well in this field. Using continuous inclination measurements 4 m from the bit, the directional driller was able to respond to changes in the well plan as requested by the wellsite geologist.

Predicting open hole data

An advanced artificial intelligence method applies neural network techniques to predict openhole log responses from acquired cased hole logs. Halliburton Energy Services developed the method through its logging and perforating product service line. This method of Chi Modeling allows geoscientists and engineers to evaluate their reservoirs at reduced cost and minimized operational risk without using traditional open hole logging methods, the company says. According to Halliburton, the results generate high quality data for direct use in net pay calculations, stimulation design, and reservoir characterization projects.

The challenge of E&P companies to improve their reservoir characterization efficiency in the face of more complex reservoir targets has led to the development of this artificial intelligence method that can be used to produce accurate and reliable synthetic triple combo data from cased hole logs to improve the decision making process.

Chi Modeling computation has been applied in the Piceance basin, the Greater Green River basin, the Pinedale Anticline of the Rocky Mountain Region, within the San Juan basin, and the Gulf of Mexico. According to Halliburton, the method resulted in an excellent correlation with openhole logs on the first wells drilled in the Pinedale field. Stone Energy said it sees excellent potential for cost savings and improved program management through the use of this technology.

Window exit capabilities

Enventure Global Technology recently announced the addition of window exit capabilities to their list of solid expandable tubular technology applications. By using their conventional openhole liner (OHL) system, the new capability makes it possible to install and expand through a milled window off the face of a properly configured whipstock.

Kerr-McGee recently used the window exit capability in the Gulf of Mexico. This successful application installed and expanded a 7 5/8-in. by 9 5/8-in. OHL system inside 9 5/8-in. 53.5-lb/ft casing. The 2,222-ft OHL system was expanded 1,964 ft below the window and allowed the operator to maintain completion size at total depth.

By integrating SET technology with other well construction methods, the company says it has installed a record number of 146 SET systems, expanded 3,654 connections and installed more than 140,000 ft of pipe for 40 operators globally.

Under-balanced drilling

Aberdeen-based Frontier Group recently completed a successful 18-month project to manage the implementation of under-balanced drilling (UBD) for Shell joint venture company Petroleum Development Oman. Frontier participated in planning and implementing the UBD operations in two of the PDO's maturing oil fields – Nimr and Saih Rawl. The UBD implementation project was deemed by the PDO as the biggest project of its type outside of North America.

UBD differs from conventional drilling because the pressure in the wellbore is lower than the pressure in the reservoir being drilled. This method avoids damage to the reservoir and results in hydrocarbon production while drilling.

The Nimr and Saih Rawl are both mature fields and have characteristics that indicate that production is not being optimized due to reservoir damage – hence the reason for underbalanced drilling.

Nimr is a sandstone reservoir with high viscosity oil. Fourteen wells were drilled to evaluate the benefits of underbalanced drilling in improving productivity in the reservoir. The wells were drilled horizontally with crude oil and nitrogen as the drilling fluid.

Saih Rawl is a carbonate oil reservoir and four six-leg multi-lateral wells were drilled to provide an evaluation of productivity improvement. The wells were drilled horizontally with crude oil and natural gas as the drilling fluid.

PDO plans to increase to four rigs drilling UBD wells during 2003.

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