Abstract
Utilization of low-density completion fluids and packer fluids is becoming more popular in oilfield deepwater operations. These low-density fluids must first meet the expected nonformation damage aspect, found with clear brine fluids, and consequently not impede future gas or oil output from wells. However, formulation of such fluids has some unique challenges to overcome in the deepwater environment. Especially for completion fluids in deepwater wells, they have to work under significant pressure regimes and low mudline temperatures, conditions favoring the formation of gas hydrates. Methanol is the only known thermodynamic hydrate inhibitor allowing formulation of a low density and hydrate protected fluid, while glycols and salt solutions can add undesired density to the fluids. On the other hand, high volatility, toxicity and flammability of methanol make this chemical a necessary "evil" in oilfield applications.
In the particular case reported here, a multiwell deepwater project located in a Gulf of Mexico (GOM) deepwater area required a low-density packer completion fluid to optimize operational requirements and the operator insisted the usage of methanol be limited or possibly eliminated. With the particular reservoir pressure and low mudline temperature, as low as 1.67°C (35°F), the gas/fluid system was severely at hydrate conditions. Commingling a Low Dosage Hydrate Inhibitor (LDHI) being a combination of thermodynamic hydrate inhibitor (THI), kinetic hydrate inhibitor (KI) and antiagglomerant (AA) with a low-density fluid was a viable solution to the problem. A novel low-density packer fluid containing a long lasting LDHI was invented for the application.
Working with the new fluid is a safer alternative; the fluid is more acceptable than the high methanol product. The hydrate-inhibited system was placed inside the annulus as packer fluid in a unique fashion and in coordination with other packer fluids. This novel placement method has been applied in multiple GOM deepwater wells. This paper highlights the development of the hydrate inhibitive packer fluid technology and its successful field application.
