Forms :: How To Get Next Value In Master Block

I created one table with out primary key like well_1 .in that table have have more than 30 columns.

SQL> select uwi,analysis_obs_no,fluid_type,top,base,date_sampled from well_1
2 where uwi ='1000 and base =2871.5;

UWI obs_NO F TOP BASE
---------------- ---- ------ ----- - -----------------------------
1000 1 G 2870.5 2871.5
1000 3 G 2516 2871.5
1000 4 G 2870.5 2871.5
1000 2 G 2870.5 2871.5
1000 6 G 2516 2871.5
1000 5 G 2516 2871.5
1000 7 G 2516 2871.5
1000 1 L 2516 2871.5
1000 2 L 2516 2871.5
7 rows selected.

i did code like this in from in search panel. in taht form i will enter uwi and base values and iwill click search button.then it will display all record values in master block .after taht i will click next button then it will display next values(all values).

i am getting all values (1 G to 7 G values).but iam not getting last 2 records when i click next button (1 L to 2 L values ).

next button

select analysis_obs_no,fluid_type
into :ctrl1.OBS_NO,:ctrl1.fluid_type
from well_gas_anal
where analysis_obs_no =(select min(analysis_obs_no)
from well_gas_anal
[code].....

i tried in SQL*PLUS like this :

select rowid,analysis_obs_no,fluid_type,rownum
2 from well_gas_anal
3 where rowid=(select min(rowid)
4 from well_gas_anal
5 where analysis_obs_no > &a
6 and uwi ='1000' and base =2871.5 )
7 and uwi ='1000' and base =2871.5
8* and fluid_type is not null
SQL> /