To address the issue of low natural imbibition recovery in horizontal wells within tight reservoirs and the challenge of replenishing formation energy during extended depletion phases

a strategy involving water injection huff and puff in large displacement horizontal wells was proposed. This approach builds on the fundamental characteristics of reservoirs and the established mechanisms of water injection huff and puff oil production in tight reservoirs. The research focused on the Chang-7 tight reservoir in Ordos Basin

employing a combination of natural and artificial cores. This study explored the range of natural imbibition and the dynamics of water injection and huff and puff across various displacements. Methods like nuclear magnetic resonance were used to analyze the characteristics of microscopic pore production

the impact of displacement on pore productivity

and the effects of soaking time. The findings reveal that with smaller displacements

mainly large pores are utilized for water injection

resulting in minimal engagement of small and medium pores. Conversely

higher water injections significantly enhance the involvement of small and medium-sized pores

thus substantially boosting the overall recovery rate. Additionally

as the simmering time is extended

the oil-water displacement effect increases

enhancing the degree of recovery through water injection huff and puff

though the rate of improvement eventually stabilizes. Numerical simulation was used to optimize the parameters for water injection huff and puff development in fracturing horizontal wells. For Well-A9

the optimal parameters were identified as a daily water injection rate of 900 m³ and a simmering time of 24 days. The field test confirmed the effectiveness of these parameters

with an initial daily oil increase of 2.11 tons

an effective period of 365 days

and a cumulative oil increase of 770 tons.