A low-cost deepwater gas development solution using subsea dehydration

Abstract

Existing solutions for deepwater gas are being challenged in the present economic environment. Surface solutions result in large facilities that are heavy and costly to build. Additionally, subsea solutions are also challenged when confronted with long distance tie-backs. A new approach has emerged—a hybrid sales gas subsea process using subsea dehydration. Existing subsea gas developments rely on either adding chemicals or heat and insulation to avoid hydrate formation. This has been very successful across short to medium tie-back distances and relatively shallow waters. Across longer distances and deeper waters, however, it can prove far less efficient and more costly—this is not the standard method to process gas either onshore or on platforms. The main way to avoid hydrates is to remove the water. Gas dehydration is a standard process operation in surface facilities. This technology now exists in the subsea environment. Active cooling is used to remove the bulk of the water above the hydrate formation temperature. A Sales Gas Subsea process is then used to produce a dry single-phase gas. Power generation and condensate export (if needed) is provided by a simple low-pressure floating production storage and offloading (FPSO) or equivalent surface facility. This process, together with an innovative hybrid development concept, is described in this extended abstract. For many gas fields, this concept can deliver a 20–40% cost reduction at an acceptable project risk.