Water injection is the most commonly used method for pressure maintenance in depletion drive reservoirs worldwide and there are numerous examples where the recovery has been enhanced significantly. However early breakthrough of injected water due to high permeability zones or thief zones mostly in heterogeneous carbonate reservoirs causes water recycling resulting in poor volumetric sweep and in turn adversely affects the oil recovery from the reservoir. A judicious mixture of proper reservoir management and development strategy may reduce the water recycling to a significant level. Sabiriyah Mauddud is a giant carbonate reservoir in North Kuwait and has been under production since last 57 years. Historical performance indicated very little aquifer support for the reservoir with no water production. A water flood pilot was initiated in 1997 when the reservoir had produced only 1% of its oil in place and pressure declined from its initial value of 3700 psi to the level of 2600 psi. Currently, the reservoir is under water flood with inverted 9 spot patterns in the crestal part and peripheral injection mainly in the western flank area. The water cut has gone up to the level of 42% after only low current oil recovery. High water cut is attributed to poor sweep efficiency due to preferential movement of water from conventional injector to producer through high permeability streaks/thief zones in the crestal area. As short term measure, a conformance plan to shut off the water contributing layers was prepared and has been introduced in the wells worked over during the period. Simulation run shows reduction in water cut by 5% by adopting the conformance plan. The new development strategy formulated for the field is to inject low and produce high from the reservoir and shifting the focus from crestal to peripheral injection. All the producers are planned to be completed with inflow control device to control the water production through the wells. The recently drilled producers are showing positive results and it is expected that the measures taken will help to maximize the benefits of water injection. The learning and the water flooding experience gained will be a valuable input for other reservoirs under water flooding.

National policy on education, various education committees and reports reiterated to implementation of free and compulsory elementary education. Right to Education Act (2009) has made education free and compulsory of children aged 6-14 to ensure Universalization of Elementary Education (UEE). But a country like India which is a mosaic of different castes, creeds and religions always remains a gap in the policy and the implementation at the grassroots level. Drop out remains a major impediment to achieving UEE Goal. West Bengal has a large portion of the Scheduled Caste population. Historically this community is deprived in terms of socio-economic development. The curse like drop out, also seen higher among these communities. In West Bengal, there has been a spatial variation of dropout of Scheduled Caste students. As the poor socio-economic condition is the major reason for the high dropout rate, the Government of West Bengal has taken various initiatives like Kanyashree, Sikhashrre to minimize the dropout rate but still, it has not been possible to achieve the zero drop out goal at school education.

This paper describes an efficient assisted history-matching (AHM) workflow that integrates production logging tool (PLT) data, streamline trajectories, and tracer data for fields with high-permeability streaks (thief zones). A field case study from North Kuwait of Sabriyah Mauddud (SAMA), a giant carbonate reservoir with more than 400 producers, is presented to demonstrate the application of the new AHM algorithm. In this field, the presence of thief zones was identified during a waterflooding period when water breakthrough occurred much earlier than expected. Data from the PLT and limited core plugs also supported the presence of thief zones in several layers of the reservoir and confirmed the majority of the water was flowing through these thief zones. Therefore, PLT data-derived thief-zone logs were used to populate the distribution of thief zones in the geomodel. However, reservoir simulation demonstrated that cumulative water production was significantly lower than the observed value. Streamline trajectories demonstrated that water was flowing homogeneously in the reservoir. Therefore, a new history-matching algorithm that integrated PLT data directly into the workflow and modified the thief-zone distribution was proposed. The workflow basically identifies the presence of thief zones at the well locations based on PLT data. Streamline trajectories from simulation and available tracer data were used to better understand the connectivity from water injectors to various producers. This information was then used to modify the reservoir model by altering thief-zone distribution. Multiple models were generated by varying the permeability distribution within the generated thief zones and the thickness of the thief zones. These new permeability models were able to produce water at the field level. First, field-level pressure and production rates were matched by adjusting reservoir properties, such as pore volume, oil API, and fault transmissibility. A Markov-Chain Monte-Carlo (MCMC)-based algorithm was used to match well-by-well production rates for oil, water, and bottomhole pressure (BHP). Two-dimensional (2D) discrete cosine transformation (DCT) was applied to the permeability layers to the DCT coefficient domain for optimization purposes. Only low-frequency DCT coefficients that corresponded to thief zones were efficiently sampled during MCMC-based optimization to converge toward an accurate distribution of thief-zone permeability to history match the production data. Therefore, a reduction in sampling space along with the improvement of connectivity helped accelerate convergence. Given the model size and complexity, the optimization converges fairly quickly. Most of the wells demonstrated an excellent match between simulation results and production data of oil, water, and BHP of more than 200 wells with significant production history. PLT data were also closely matched with the simulation production profile at the wellbore. Streamlines of water for the history-matched model demonstrated the water had been flowing through the thief zones. The history-matched model can be further used for better reservoir management and waterflood optimization to improve oil recovery.

A mature and congested field with multi-stacked sandstone reservoirs has been developed through depletion drive for 50 years and more recently with peripheral water injection. Currently, the field performance shows rising water-cut in some reservoir units and pressure depletion in others, but still has significant remaining development potential. A field development plan has been established to economically produce bypassed oil, driven by the analysis of the historical performance data for the different reservoir units. Integrated analysis of historical data and development decisions identified the subsurface and operational drivers behind the increased water-cut and differential pressure depletion. This paved way for developing clear recommendations for the major development decisions on well and completion type, well spacing and waterflood strategy. Oil production type curves generated for each reservoir unit using recent infill drilling historical production data helped establish the preferred development phasing and production forecasts. Urban planning is a key enabler to realize value from the future development of the field due to surface congestion; therefore, the new wells have been allocated to multi well pads. The detailed analysis focused on each area of the field, complemented with saturation logs and dynamic model, helped in determining the long-term well requirements and their locations targeting bypassed oil. The integrated study generated a rolling development plan covering the field life cycle to accelerate oil production and reserves maturation and improve the reservoir pressure and sweep. Each new well has been assigned a primary reservoir target and a confidence level for the target reservoir to enable phased implementation of structured infill drilling to reduce well spacing starting with high confidence wells. New water injectors were added to the reservoir units that have limited aquifer support. Integration of the well pad allocation and development schedule with the pad construction schedule helped identify and mitigate against any surface related showstoppers to the planned well locations and the development schedule. As a result, more than 130 new development wells were added to accelerate oil production and increase production rates. This integrated study manifests the power, efficiency and value from brownfield data driven analysis to capture lessons learned from evolving wells and development concepts applied in a complex field over six decades. The workflow enabled the delivery of an updated field development plan and production forecasts within a year through utilizing data analytics to compensate for the recognized limitations of subsurface models. Urban planning and multi-well pad drilling concepts alleviate the impact of drilling constraints.

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