The learning curve has evolved in the last few years for operators in shale plays. Early wells started with relatively large cluster spacing and small proppant volumes resulting in suboptimal initial completions. Over the years, perforation cluster spacing has declined. Consequently, the number of hydraulic fracturing stages has increased. The total proppant pumped per lateral foot has also increased. The majority of the existing wells were completed with geometrically spaced multiple perforation clusters per stage. Sometimes more than six clusters per stage have been employed. Studies have shown that one-third of these perforation clusters are not productive (Miller et al., 2011). Noncontributing perforation clusters could be due to not initiating hydraulic fractures, insufficient proppant placement, or loss of near-wellbore connection due to over-flushing or severe drawdown. Furthermore, during the development phase, the depletion from parent wells leads to asymmetric hydraulic fracture growth on closely spaced infill wells. Parent wells may also be negatively impacted due to hydraulic fracture interference from new completions. These factors have led to poor hydrocarbon recovery factors, sometimes less than 10% in horizontal shale wells.Recovery factors from existing wells can be improved through restimulation. Candidate selection is a key in achieving economically successful restimulation. Restimulation of appropriate horizontal shale wells resulted in significant production uplifts based on early field results. Designing a fit-for-purpose restimulation treatment is dependent on initial completion, offset well distance, infill plan, and, above all, economics. On top of the design aspect, operationally achieving effective restimulation on long horizontal wells with tens of perforation clusters is a challenging task. Thus real-time monitoring and control is a key for field execution.This work uses an integrated petrophysical, geomechanical, hydraulic fracture, and reservoir modeling workflow and field observations to develop restimulation strategies for improving hydrocarbon recovery. This integrated workflow includes a multistep calibration process to reduce uncertainty. One of the key calibration steps is to model hydraulic fracture growth accounting for local geological heterogeneity and match with observed treatment parameters and microseismic interpretations. Another critical calibration step includes automatic gridding of hydraulic fracture geometry to run numerical reservoir simulation to match realized production results. Reservoir pressure distribution at the end of the production history is used to recalculate stresses for modeling the refracturing scenarios.Multiple practical refracturing scenarios were constructed for addressing near-wellbore connectivity issues and ineffective drainage along the lateral. Creating new surface area in undrained rock and restoring productivity of existing hydraulic fractures resulted in higher recovery. Higher proppant amounts in undrained rock on one well pad or late...

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It is a common practice to evaluate an injection pilot before a field-level implementation of waterflooding, but this requires early investment in facilities and construction time. An alternative solution is proposed as a modification of the dump flooding concept: Produce water from a low-salinity aquifer and inject it into an oil reservoir within the same well, using a closed system. The modification of the conventional dump flooding design consists of adding surface monitoring and control capabilities, which for this mature field is a local regulatory requirement A comprehensive process for the completion design considered reservoir, well and operational conditions as both new and existing wells were considered as candidates for these completion systems. The design consists of a concentric completion with packers to isolate both the water aquifer and oil reservoir. Water is produced from a deeper low-salinity aquifer with excellent water quality through an Electric Submersible Pump (ESP) that also serves as an injection pump. At surface, the water rate is measured by a flowmeter and then injected into the same well through a concentric string to a shallower oil reservoir for secondary recovery. A simple closed-loop system at surface eliminates contact with oxygen, minimizing future corrosion problems. The high quality of the water (low salinity, without solids, O2, H2S or Fe) eliminated the need for water treatment. Four wells have been successfully completed using this design, currently injecting at the required rates without presenting any functionality problem. Additional three wells are in schedule to be completed in order to accelerate waterflooding implementation in areas either remote or environmentally sensitive with no nearby water source. In these areas, implementing a waterflooding conventional pattern that requires connecting water producers and injector wells would require lengthy permission processes for long high-pressure lines and additional time for the construction of those water transport pipelines. The completed modified dump flooding wells decreased the implementation time of the waterflooding pilot project from 2.5 years to 5 months. Additionally, the environmental footprint and facilities investment has been reduced by an estimated 90%. This is the estimated cost savings when comparing the investment in dump flooding well construction versus conversion of existing wells to water producers or injectors and the investment in facilities, including water treatment plants, to connect those wells. This paper presents the main design and operational considerations before execution, deployment challenges, and lessons learned and recommendations from the execution of the first campaign

Romgaz, the Romanian national gas company, and Schlumberger joined forces in 2003 through a 15-year collaborative agreement for the rehabilitation of the Laslau Mare gas field. One of the main focuses of the agreement is the acquisition of data in order to develop a deeper understanding of the field, and thereby optimize the field management plan. After a First Work Program campaign, executed in 2004—2005, field production was increased by 40%; the result of workover jobs performed and elimination of surface network bottlenecks. In addition to a portfolio of rig workovers, the approved Work Program for 2009 included an aggressive and challenging campaign of rigless interventions to optimize and maintain field production. The total production from the field has increased by 17% as a result of this rigless campaign, which mainly comprises coiled tubing interventions for water unloading (identified by slick line fluid level measurements) and the verification of the mechanical status of all active wells in the field. An additional 6% production increment was achieved with optimization of well soaping schedules, which is the current continuous water lifting method in Laslau Mare field. The encouraging results of the rigless campaign and the additionally achieved incremental production rate were realized by implementation of the production optimization workflow outlined in this paper. This workflow aims at close monitoring of individual wells, identification of production gaps and intervention opportunities. Finally, well candidates are selected based on economic analysis. The success of the campaign is demonstrated by the production gains and the short payout times achieved. The entire rigless intervention program paid out in a couple of months. This paper presents the optimization workflow, its implementation to select candidates for the rigless campaign and the production and economic results of the executed work in 2009.