Abstract

The Gulf of Suez Petroleum (GUPCO) is the largest offshore oil producing company in Egypt, producing over 330,000 barrels of oil per day from 78 offshore platforms in the Gulf of Suez. The majority of this production comes from sandstone ranging from Cambrian to Cretaceous in age. This paper discusses GUPCO's use of two stage rotating liner technology to optimize production cementing performance. The two stage rotating liners have been used for two primary applications in the Gulf of Suez. The first application is production liners in the October Field, due to loss circulation, which often occurs in the Nubia sandstone producing horizons. The two stage cement job enables zone isolation within the Nubia, the opportunity to isolate the overlying Nezzazat section and obtain a liner lap seal. The use of rotating liners in the October Field presents several technical challenges due to hole stability issues related to the existence of alternating lithology and pressure regimes in deviated wells. The second application of this technology is in the Morgan field, where the second stage cement job is used to provide adequate collapse resistance for the mobile salt sections in the South Gharib formation. This application saves the rig time and additional cost normally associated with running a scab liner inside the 9-5/8" intermediate casing.

Introduction

Drilling operations in the Gulf of Suez are performed from jack-up drilling rigs. The conventional well bore design includes 9-5/8" casing in the intermediate hole section and 7" cemented liner in the production hole section. The intermediate hole section is drilled with a 13.0 to 14.5 ppg drilling fluid, usually oil base mud. Some of the southern Gulf of Suez fields experience strong salt water flows that require a 17.0 to 18.0 ppg drilling fluid. The intermeate casing isolates significant salt, anhydrite and shale from the production hole section.

The production hole sections are normally to sub-normally pressured primarily due to depletion. The reservoir pree in wells drilled today generally ranges from 3.0 to 7.0 ppg, with multiple pressure regimes in each well bore. Some of the shales are 9.0 ppg original reservoir pressure. These Wells are drilled with an invert oil base mud contain lost circulation material. The amount and type of lost circulation material in the mud has effected the ability to have 100% successful cement jobs. The effect of different types of LCM and varying concentration has not been determined at this time. Rotating two stage liners are run and cemented to provide zonal isolation and to achieve a seal across the Siner lap.

Preplanning and Preparation

A detailed liner running and cementing procedure is written for every well. This procedure is written at the onshore base by the engineering staff with input from the liner company service and engineering personnel and the GUPCO offshore drilling supervisors.

The ability to rotate these liners depends on the rotational torque which is a function of the hole geometry, friction factors and centralization. The maximum dogleg severity which a liner has been rotated through in these two stage applications is 7.4 degrees per 100 feet. Most of the well are planned for less than 5 degrees per 100 feet dog leg severity.

The friction factors are determined by recording up and down drag and rotational torque during connections while drilling the entire hole section. The torque and drag values are used in a commercial torque and drag program to determine the cased hole and open hole friction factors specific to the well. The calculated friction factors are used to verify in advance that the liner can be rotated.

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