Low permeability porous carbonate rocks occupy a certain proportion in the Middle East. Horizontal injection-production well pattern development is often adopted. Due to the influence of well type and wellbore, reservoir dynamic monitoring is mainly based on conventional daily measurement data, well test and pressure monitoring. Therefore, it is particularly important to combine well test interpretation with production dynamic analysis to diagnose the main control factors and production characteristics of this type of reservoir. In this paper, the point source function is used to obtain the pressure variation function of a horizontal well in infinite formation with upper and lower closed boundary. The difference between the horizontal well test curve of A reservoir and the typical horizontal well test curve is compared and analyzed, and the abnormal well test curve of horizontal wells is characterized by a linear flow phase with a slope of 1/3 or 1/4. The abnormal well test curve accounted for 33.34%. The main influencing factors are the permeability around the well and the well trajectory. By combining well test interpretation with dynamic inversion method, the correlation between well test interpretation and dynamic characteristics of horizontal wells with different characteristics is classified and clarified. The main controlling factors that affect the difference in the water injection development effect of different horizontal wells are further clarified, and provide an important reference for the adjustment of injection-production parameters and the optimal deployment of schemes.

Seawater flooding is popular for carbonate reservoirs in offshore oilfields and seawater is sometimes the unique choice of injection water source due to the lack of surface water supply. Seawater is injected into reservoirs to maintain reservoir pressure after water treatment for technically and economically effective field development. Uneven injection and production in B oilfield caused unbalance of pressure distribution and poor injection performance. It is essential to improve the injectivity of single well to a satisfied level through a integrated workflow on the basis of performance analysis, brine compatibility study, core flooding experiment, strategy and solution optimization. In this paper, the injection status has been analyzed and the decisive impacting factors were given including formation properties, stimulation activity, the brines compatibility and pre-treatment of injection water, which play a very important role in injection performance sustainability as the seawater injection continues. Scale modelling was done with formation water, mud filtrate, injection water and stimulation fluid for self-scaling assessment. Mixing experiment of two of the brines of four introduced at either atmospheric or reservoir condition. Core flooding experiment was carried out with formation water and filtered injection water after critical velocity for core flooding is confirmed. Then the injectivity for each wells have been analyzed at different locations of the reservoir with different formation properties, solutions have been subsequently put forward and the improvement on injectivity of injectors before and after the stimulation or even re-stimulation and the effect of cleanup after the stimulation was also compared. It was concluded that injectivity could be enhanced through stimulation and the cleanup after stimulation and the sulfate should be removed or reduced in the process of the pre-treatment of injection water from the remote terminal to ensure desirable water injection and production performance.

The permeability of the ultra-low permeability bioclastic limestone reservoir in Middel East A Oilfield is about 5md. The pore structure of the reservoir is in multimodal mode and has strong micro heterogeneity. The single well productivity was low and it was difficult to sustain production after the vertical well development was adopted in the early stage, and it has been gradually transformed into horizontal well pattern at the flank area. However, the reservoir pressure and production declined rapidly, and the development effect became worse. Through the combination of reservoir micro-characteristics and macro-production performance characteristics, this paper clarifies the ultra-low permeability bioclastic limestone oil displacement mechanism and remaining oil distribution law under the micro-macroscopic dual scale, and clarifies the reasonable well spacing of vertical well pattern and horizontal injection-production well pattern. Based on the differential single well performance characteristics and water injection development mechanism, the injection-production connectivity evaluation model based on rapid numerical simulation is established, the regional differential injection-production strategy is formulated, the injection-production optimization adjustment criteria are established, the establishment of effective displacement system for the reservoir is supported, and the adjustment of more than 280 producers have been carried out in 2020-2022. The daily oil production of a single well has been restored from 307 barrels/day in 2019 to 483 barrels/day in 2022, and the water cut is reduced from 27.1% to 22.1%, the reservoir pressure recovery of 496psi provides important experience guidance for the scale benefit production of such tight bioclastic limestone reservoir.