Recently two multilateral horizontal wells have been completed offshore using dedicated multistage hydraulic fracturing completions. The first well, located in the Central North Sea (referred to as ML-CNS), was stimulated using acid fracturing; while the second well, located in the Black Sea (referred to as ML-BKS), was stimulated using proppant fracturing. This paper presents the different drivers, challenges and lessons learned for each well while emphasizing the well construction and stimulation methodologies developed for the different reservoirs and field characteristics.
The field development drivers for drilling and completing these offshore hydraulic fractured multilateral wells, a first of their kind globally, was different for each case. The objective of the first project, initially considered uneconomic, was to engineer a technical solution for completion and production of two separate reservoirs with only one subsea well. The second project was seeking to optimize infill drilling from the last available slot on the offshore platform to maximize reservoir contact and production in the same reservoir. ML-CNS was a TAML Level 2 completion with a 14-stage, 5 ½" multistage completion run in each lateral and set-up for sequential acid fracturing. Operationally, the first lateral was drilled and stimulated, followed by the drilling and stimulation of the second lateral, using the drilling whipstock to navigate through the multilateral junction. ML-BKS was a TAML Level 3 completion that had a 6-stage, 4 ½" multistage completion installed in each lateral, which were proppant fractured following a sequence designed to minimize the jack-up rig time required. Both legs were drilled and completed prior to starting the stimulation, access to either lateral was achieved with the existing workover unit on the platform by manipulating a custom designed BHA.
The lessons learned from the first project executed in the North Sea were able to be transferred and applied to the second project in the Black Sea to allow for a more efficient and confident completion solution. Led by varying economical and regional constraints, the key factor for both wells centered on delivering operationally simple and reliable multilateral completion designs to economically meet the field development strategy in place.
To the knowledge of the authors and following subsequent literature research, both wells are a worldwide first for an offshore multilateral well completed with multistage acid fracturing and multistage proppant fracturing, and together they represent a new trend in cost-effective offshore field development through well stimulation. The successful case studies for both wells with the combined analysis of the benefits, challenges, and lessons learned will provide a guide and instill confidence with operators who find this approach beneficial with a view to applying it in other assets.
A new proppant exhibits a neutrally wet surface, which does not have a preferential affinity for oil, gas, or water and therefore will not promote the preferential entrapment of any phase within the proppant pack. Bitumen is so viscous that the ultraheavy crude oil is often compared to peanut butter.
Through data gathering, machine learning, and the use of a supercomputer, a non-profit organization in Texas is seeking to boost oil and gas production on land owned by the states’ two largest university systems. This paper reviews two newly developed novel completion systems that significantly reduce time spent performing multistage stimulation in environments where cost and consequence of failure are high.
Driven by a recovery in well completions and increased proppant loading per well, the market for raw fracturing sand is expected to grow by more than 4% annually through 2021, an industry research study says. Crude oil production in the United States is expected to approach 10 million B/D in 2018 and surpass a previous high achieved in 1970, according to the latest US EIA forecast. A global energy model estimates the long-term energy mix, including solids, liquids, and gases, that will satisfy energy demand to the year 2040.
Induced seismicity from the injection of fluids into the earth remains a significant concern for oilfield activities such as saltwater disposal and hydraulic fracturing operations. The number of induced earthquakes occurring in the oil and gas producing regions of the Central United States and Western Canada has been declining over the past few years, highlighting the successful implementation of improved regulations and effective operational practices. However, technical engineering and geoscience challenges remain. This opening session will explore the current state of learnings and progress since the last workshop in November 2017, and highlight forward opportunities and challenges. Differences in geology, industry practices, population, politics, and other factors lead to various regulatory responses and requirements.
Sourcing water for large multifracture stimulations in west Texas is a well-known constraint on oil and gas activities in the area. A 6-month pilot operation demonstrated that produced-water reuse is technically feasible and can be a cost-effective solution. This paper summarizes the benefits of using a bipolymer crosslinking system in environments where water quality cannot be guaranteed. It also demonstrates the yielded cost savings per well that are achievable when reusing 100% produced or flowback water for hydraulic fracturing. This paper reports the completion of a two-lateral well in the Williston basin where produced water (PW), filtered but otherwise untreated, was used throughout the slickwater and crosslinked components of approximately 60 hydraulic-fracturing stages.
In hydraulic fracturing, the use of diagnostic-fracture-injection tests (DFITs) can provide valuable information. This paper offers an analytical model for estimating the transient temperature at a given depth and timestep, for computing the BHP. To achieve optimal production from unconventional reservoirs, it is useful to determine the permeability, pore pressure, and state of stress of rock strata. This paper attempts to describe some of the common problems and to help prevent some common errors often observed in diagnostic fracture injection tests (DFITs) execution and analysis.
An area of great interest to those researching flowback is the interaction of water and salt inside the shale reservoir. After a well is stimulated, the flowback fluids tend to show a rising concentration of salt that falls back to near zero over time. Most shale producers in North America have given little thought to the flowback stage following hydraulic fracturing. Others have come to realize it represents a valuable opportunity to learn more about their wells. On the far end of the flowback spectrum is a completion process called soakback.
This paper summarizes the benefits of using a bipolymer crosslinking system in environments where water quality cannot be guaranteed. It also demonstrates the yielded cost savings per well that are achievable when reusing 100% produced or flowback water for hydraulic fracturing. Analyzing the properties of produced water is a difficult process because of the extreme levels of suspended and dissolved particulates contained in it, and a chemistry profile that is in constant flux. In this study, samples of flowback water and downhole shales are analyzed to investigate the mechanisms controlling the chemistry of flowback water. This paper details the experience of using new stabilized crosslinked-fracturing-fluid systems in the Permian Basin using borated produced water.