Swellable Packers in Unique Horizontal Completions Solves Difficult Challenges in Offshore India Vasai East Field

Abstract

Oil and Natural Gas Corporation (ONGC) operates the Vasai East Field in western offshore India. The reservoir is challenging to drill and complete because of the inherent risks of gas and water coning, permeability differences, and declining reservoir pressures. An innovative horizontal completion strategy for new wells to meet the many unusual challenges was required. The need for appropriate zonal isolation was identified after the wells in the Vasai West Field had been completed without segmentation in the open hole. The requirements included:○Oil production without breakthrough of gas or water○Effective hydraulic seal in washed-out hole conditions○Contingency options for intervention, if needed○Equipment to withstand high bottomhole static temperature. This paper describes how the challenges were met using swellable-packer, high-temperature isolation systems placed between perforated tubing/sliding-sleeve circulating devices and blank pipe spaced out across the oil-bearing zones. The swellable packer systems were located at the ends of each facies change to isolate the local high-permeability zones. Swellable packers use expanding rubber around the packer mandrel that expands to seal the annulus and create a permanent seal when it contacts liquid hydrocarbon or water in both cased or openhole environments. Five wells have been completed in Vasai East field to date with swellable packers in conjunction with pre-perforated liners or sliding sleeves. PLT logs have been run in one of the wells post completion, and isolation has been verified. Low water cuts and low gas/oil ratios (GOR) also verify that the packers isolate the various sections of the wells as planned. On the success of these completions, this technology is currently being planned for ONGC's completions in other fields. Introduction The Vasai East Field is located in the Heera-Panna-Bassein block and falls toward and northeast of the main Bassein field about 80 Km west northwest of Mumbai city (Fig. 1). Water depth varies from 40 to 50 m. As per the latest geological model, the field has an average oil column thickness of about 28 m trapped between the gas cap above and aquifer at bottom. The field extends over an area of 54 sq. km. Vasai East field was discovered in 2001 and had continuously declined in pressure due to gas production from the nearby Bassein field. Both the fields are hydro dynamically connected through a common aquifer (Fig. 2). The production targeted was from a thin-oil column trapped between a gas cap and water at bottom in a high-temperature reservoir. The field had been plagued with problems from severe mud loss that had occurred during exploratory drilling in the field. Also, since the oil is between the gas cap and aquifer at bottom, the horizontal drain-hole placement was critical to control unwanted gas/water production. The Vasai East Field is hydro-dynamically connected with the main Bassein field through a common aquifer, which is depleting due to constant gas production. Therefore there was an urgent need to quickly develop this field. To keep pace with the quickly depleting reservoir pressures, efforts were made to expedite the development scheme for the exploitation of oil from this field. The Vasai East Field is separated from the main Bassein field by a low axis at the Bassein formation level.

Research Progress of Elastomer Materials and Application of Elastomers in Drilling Fluid

“…Expansion causes changes in geometry, density, hardness and other properties [ 58 , 59 , 60 ]. Water-expanded elastomers absorb saline solution and expand through a permeation mechanism, while oil-expanded elastomers absorb hydrocarbon and expand through a diffusion process [ 61 ]. The swelling ratio depends on the temperature, pressure, elastomer type and fluid composition.…”

Some downhole applications of swelling elastomers in oil and gas wells

“…Swellable elastomer can also be used with open-hole, cased-hole, horizontal well, and solid expandable tubular (SET) technology as a completion tool. 13,14…”

Experimental Investigation on the Penetrability Mechanism of Gel Slug During Well Completion Processes

“…Generally, it is necessary to use killing fluid or blow out pressure to ensure the safety of downhole operation before drilling and completion. − However, it is inevitable to invade reservoirs in killing operation, resulting in a sharp decline in permeability and oil and gas production due to the change of physical and chemical properties of oil and gas reservoirs and plugging of pores by solid particles. , According to the data statistics, each well killing operation can reduce production by 20%. , Meanwhile, the pressure blow-out will lead to the pressure drop of local formation, damaging the formation structure and well pattern pressure distribution , and reduce the formation productivity. Therefore, killing and blowout operations are not conducive to the sustainable development of oil and gas resources but also not beneficial for the development of low permeability and low production of sensitive reservoirs.…”

“… 21 , 22 According to the data statistics, each well killing operation can reduce production by 20%. 23 , 24 Meanwhile, the pressure blow-out will lead to the pressure drop of local formation, damaging the formation structure and well pattern pressure distribution , and reduce the formation productivity. Therefore, killing and blowout operations are not conducive to the sustainable development of oil and gas resources but also not beneficial for the development of low permeability and low production of sensitive reservoirs.…”