Multilateral Offshore Well Completed With Multistage Proppant Fracturing
Authors: Feder Judy 
Published: April 2020

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 194324, “The World’s First Offshore Multilateral Well Completed With Multistage Proppant Fracturing: A Case Study From Offshore Black Sea,” by Andrew Tomlins, OMV; Joel Conrad, SPE, Packers Plus; and Bogdan Bocaneala, OPECS, prepared for the 2019 SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, 5–7 February. The paper has not been peer reviewed.

The complete paper discusses the successful execution of the first offshore multilateral well completed for multistage high-pressure proppant stimulation, according to the authors, in the Black Sea offshore Romania. The authors discuss the drivers that led the operator to trial a multilateral well; the selection, planning, and final completion solution; and the lessons learned.

Field Background

Lebada Vest, located 95 km offshore northeast of the city of Constanţa, is the largest offshore Romanian oil field currently in production. It was discovered in 1984 and has been in production since 1993, and thus now faces the challenges and strong investment requirements associated with a mature field. Hydraulic fracturing has been used in the field’s low-permeability-formation wells since 1992, mainly in vertical or slanted wells.

Completion Challenge

With only one platform slot left and a significant undrained area of the reservoir, the operator had to maximize hydrocarbon recovery through a single well which, because of pressure to increase daily production, had to be finalized in 1 year. Building on field experience gained since 2008 in multistage proppant stimulation, a detailed screening and evaluation of multilateral completion technologies was performed. The focus was on developing a concept that would minimize risks during execution while meeting cost and lead-time objectives, which necessitated customizing the chosen Technology Advancement for Multilaterals (TAML) Level 3 completion design and installation methodology.

To maximize rig-time efficiency, the well was executed in two phases:

Drilling and lower completion installation of both branches with a drilling rig

Stimulation and upper completion installation with the platform’s workover rig

With six stages in each lateral, the high-pressure stimulation was executed by a converted supply vessel in four sailings, necessary to reload materials. To meet the delivery schedule, ensure simplicity, and leverage operator experience, the completion was undertaken with no dedicated multilateral hardware. Instead, the operator used standard, multistage, stimulation openhole completion equipment and appropriately engineered bent joints to exit the main bore.

With initial production rates higher than anticipated, the well proved considerably more economical than drilling two horizontal wells with equivalent reservoir coverage. The success of this well serves as a proof of concept and provides increased confidence in delivering reliable, cost-effective, multilateral wells, even under tight time constraints and in areas or with operators with no history of multilateral completions.

Identifying Multilateral Completion Requirements

The operator’s field-development team investigated single, dual, and trilateral well-design feasibility against agreed design criteria. The principal objective was to maximize the chance of success through an appropriately risk-minimized design using standard, field-proven tools and techniques. Completion-design criteria were carried from the previous (single-lateral wells) field-development campaign in terms of production objectives, intervention capabilities, and logistics. The complete paper discusses the effect of general well design, junction, stimulation, intervention, rig strategy, and logistics and experience on the completion requirements.